When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
yes and no, theres legends about more power but dyno's don't really show it (the earlier engines had the 'Coscast' and later catalyst engines had KS (GM) heads, cat engines had a few hp less with different fueling & cams so maybe this is more to do with the legend....
Ha ha maybe, I just thought it was an interesting yardstick.
I think I found the issue with the WI system. Port 2 nozzle's one way valve was being bypassed by an o-ring not sitting quite right. Need to go on a test drive to test again but I am pretty confident that was the issue.
I've continued to dial in the simulation model. I got the fuelling set up to 11.5AFR and set the surface area options. It bought the sim bang into line with whp / wlbft with my very first dyno session on the stock pulleys, and testing the new pulleys at 35degC air temp netted within a hp of the second session.
PR on the sim is down to 2.08PR across peak torque but then drops off to about 1.95PR by 7krpm. I think I just need to properly measure my cams at the valve and see how that changes the PR curve.
I am finding though that as I increase the accuracy of the sim, the power difference any sort of larger valve or porting gains decreases. I've reached the point were for this project I am not going to pursue the flow bench. I think this is something best left for a future project.
I am going to give the intake a basic bowl cleanup, SSR smooth and a deshroud. The exhaust side I am going to use the +1 valves because I already have them, with some port work particularly around the guides. I don't think I need a flow bench to do this, which cuts a huge amount of time and work out of the project. I can always look again next year if I want to.
The big hitters that keep showing decent gains, particularly when combined is sc intake pressure and temp, and compression. Here is a table of my latest sim work results. I plan on running the rev limiter at about 7500/7600rpm so peak whp will be in the middle of the 7 and 8krpm calcs.
They seem broadly sensible. My WI testing on virtual dyno was showing an approx 10lbft bump across the board pretty reliably on the old head and adding that to the non WI figures in the table they correlate pretty nicely. Interesting that the 5krpm torque drops slightly when the intake was ported, it was moving peak torque up the rev band slightly.
Hopefully the no filter dyno testing at the end of the month shows the gains I think it should and I can work from there.
Update on the simulation, with some interesting results.
Main step has been measuring actual valve lift of both my custom cams and the stock BP4W/BP5A cams. They look far more like the automatically generated profiles in the sim than my previous incorrect measurements.
Fair bit more area under the curve on my custom cams.
Running the tests again with the same / similar variables as before gave the following results
There is a few interesting things going on here.
First, the baseline old pulley figures tie in really nicely with my first dyno session.
In the sim going to my big exhaust makes naff all difference. But the sim also reckons that the my old small system has 0.1 bar average backpressure - which I know was not the case, it was bigger than that. This may be the simplification of testing effectively straight piped showing itself.
Running the stock BP4W head (stock cams, CR9) drops me 3lbft of peak torque, and loses a pretty big chunk of top end power over the 9.5CR custom cam head I was running previously. In real life I tend to agree, it feels like the figures suggest. This is also the cylinder head setup that the 8krpm power is lower than the 7krpm.
Removing most of the intake restriction nets good gains in torque and power as before. I did keep a bit of restriction, because I don't think I will remove it entirely with any upgrade.
Pumping up the comp to CR10 again gave good gains across the board.
Interestingly adding the +1 exhaust valves and doing an exhaust port gave a good jump in power above peak torque this time, in the last batch of testing the gains were far smaller.
Really interestingly then, substituting my custom intake cam with the slightly shorter and lower lift stock BP5A intake cam it gained 3lbft of torque at 5krpm, only lost 1hp at 7krpm then lost 5hp at 8k(above my limiter anyway). It pivoted the power band slightly lower in the rev range. I think this would be a faster overall setup for my rev limiter / use.
I then modelled a cam with the same duration as the BP5A, but with the lift of my custom cams and it kept the torque at 5k but also kept the top end hp of my current custom intake cam. I'll have to think about it, my heart says yes my wallet says no.
The last two tests are with +1 intake valves added with a full intake porting. You can see this tips the power band towards the higher rpms, at the expense of mid range. Not something I am going to pursue.
I did some analysis on why the shorter duration intake cam worked better than my current custom intake cam (for my rev range) and this is what I found. Basically reduced reversion just before the intake valve closes with the shorter duration cam, meaning better overall cylinder filling at these rpms than the longer duration intake cam, and a higher mass flow.
Bit more comparison work, this time on +1 intake valves and intake porting
All traces are done with the same cams, cam timing and +1exhaust valve with porting. The difference is one trace also has +1intake valves and intake porting and the other has a standard intake valve and intake port.
Left graph is at 5krpm. The trace with the deeper negative dip in mass flow rate, and slightly lower overall mass flow rate is the big intake valve.
The big valve mass flow has a bit of a wild ride on the way up to peak mass flow, the first crest coincides with the closing of the exhaust valve, indicating that the larger valve allows for greater exhaust scavenging. Interestingly the mass flow on the exhaust only shows a slightly higher mass flow indicating most of this extra air charge does stay in the cylinder even at 5krpm.
Not sure what the second crest is about, but the big valve does go on to the higher peak mass flow.
The standard valve is like the tortoise - on average it just about wins out, with a higher velocity and slightly higher mass flow throughout the majority of the valve closing period. I think it is this extra velocity, as well the slightly smaller curtain area at the same lift and worse flow coeff from lack of port (seat) work that gives the higher resistance to reversion at intake valve closing. The cumulation is a higher mass flow for the standard valve and port at 5krpm.
At 8krpm the reversion is less severe for both valve sizes, but more so for the +1 valve so the disadvantage here is lessened. I think the generally higher air velocities at high rpm give the charge enough inertia to keep filling and avoid reversion despite the piston coming up the bore. The increased mass flow on valve opening of the +1 valve gives it the overall edge on average mass flow gives it the edge on power.
Be interesting to see if I do the model as a normally aspirated engine whether I see the same results or not.
Some more experimentation on the sim
I played about with the parametric optimisation tool, specifically with regards to cam positioning. The sim likes an advanced intake and exhaust cam, this won me 0.5lbft at 5k and a hp in the top end for a like for like setup with the original 108 or 110 / 110 cam settings I was using previously. Not much, but I will take it.
I have simplified the table above to cut out the variables that are settled. 10CR, my big exhaust, 11.5AFR, optimised intake tract are applied to all the setups above.
The first two tests show that running a +1 intake valve with a larger intake port - modelled around the Na8cgee developed port. You can see the torque drops slightly at 5k, within a hp at 7k but at 8k you start to see the gains of the larger intake setup.
Test 3 shows the result of the cam timing optimisation, I made slightly more torque and equalled 7krpm power with the stock BP5A cam when compared to my hypothetical high lift short duration cam, although the bigger lift cam started pulling away slightly by 8krpm.
Next up, and most interestingly I applied the improved flow coefficients from Schercheeroo's analysis around a basic bowl cleanup, SSR and deshroud, but leaving port CSAs as per stock.
You can see in test 4 that torque stayed the same at 5k, but there was a reasonable gain in top end power, 3hp at 7krpm and 4hp at 8krpm. What is interesting is you get the top end gains but without the trade off of losing torque in the midrange, like the larger port. Midrange and power at 7k was above the of +1intake valve large Na8cgee port, only losing out at 8k. It shows that even though I am supercharged I still need to be careful of port cross sectional area vs intended powerband. I think this goes against some of the information you can read which is along the lines of 'doesn't matter what size your ports are when supercharged'.
The last 3 tests then throw the short duration high lift cam and +1 intake valves at the SSR / deshrouded / stock CSA intake port. For once the +1 valves don't loose a little midrange - indicating it was the port size causing this.
Unsurprisingly the highest performing setup is with the high lift cam and +1valves - but this represents a large amount of expenditure for marginal gains. I think the sweet spot is the stock BP5A cam, with the SSR / deshrouded / stock CSA port on the intake side, with +1 exhaust valves and exhaust porting. Sim says this should net 240.5lbft at 5krpm, 294whp @ 7500rpm. The all out setup would make 241lbft / 297whp @ 7500rpm.
So really next steps are to see if I get the figures the sim reckons on the dyno next week with and without the air filter on, which is 224lbft / 256whp with filter, 230lbft / 267whp without filter, and start work on the head
Another piece of interesting info I thought I would drop in.
This is with regards to intake runner length. My current intake manifold uses a very short (50mm) runner before the start of the port in the head. I ran a parametric test for manifold runner lengths up to 290mm, to see if runner length affected torque and power on my simulated supercharged engine.
See results below:
You can see in the top graph BMEP varies quite dramatically, particularly around peak torque, 5krpm.
Based on the scoring weightings I gave 210mm would actually be my optimal runner length. This delivers middle of the pack peak torque but carries that torque nicely through the top end.
My current 50mm length is the worse for peak torque, but picks up in the top end nicely.
Some lengths were very strong at peak torque, but those were the lengths that rolled over more at high rpm.
The second graph shows the hp / tq traces of both my current 50mm manifold and a hypothetical 'best' 210mm manifold. A decent chunk more torque in the midrange on the 210mm with no loss over the 50mm at the top end. Shame it would mount my supercharger in the wheelarch, but there we go.
Thought it was interesting to show that these dimensions do matter, atleast in the simulation.
Intake side I raised the roof of the bowl behind the valve guide by about 2mm to get a larger radius blend into the seat, so the turn is gentler on the long side of the port. The CSA is still expanding towards the seat from the guides, I haven't hogged out much really. I have also blended the SSR. Conscious I want to keep a tight port based on the sim findings, just improve efficiency. Need to remove the guides to blend the bowl properly into the high speed section of the port in front of the guides. The only thing I am going to touch upstream of the guides is matching the port opening to my manifold when I come to put it on the car.
Exhaust is a little more dramatic, removing the valve guide 'hump' to ensure the CSA of the port is basically uniform the whole way through. Again need to remove the guides here to properly blend that area still. Also the exhaust will be having the +1 valves cut in so will require further finishing.
Next up will be a light deshrouding making sure I outline my 84mm bore on the head first. I don't want to remove too much material in the combustion chamber, as it will drop compression.
Then moving onto removing / having the valve guides removed.
Pretty disappointing day at the dyno tbh, even though I was prepared to be disappointed anyway. I wanted the car to make 256whp @ 7k rpm to be inline with my simulation work.
It made 230whp, 268 at the crank. A fair way down on last year despite the colder weather. I was at a different more local dyno, so there is potential for variation there, and as per previous posts above I wasn't expecting a big jump in numbers. But I wasn't expecting a loss in power. The testing was done on a 'ramp rate' rather than just a straight power run so I need to do some digging on that to see if that could explain anything.
Anyway my tear ducts are empty now so I will move onto better news.
Testing without the filter, but with a bellmouth resulted in the gains my simulation predicted (just from a lower starting point). Swapping to the bellmouth netted roughly 10hp by redline, 10kPa boost pressure and decent separation on the dyno chart from 4500rpm up. I think the reason I did not see these gains last time is because just a raw throttle body opening isn't actually very good for flow. It has a sharp edge with almost no radius where you would normally attach the pipework and I wouldn't mind betting a pretty lousy flow coefficient / effective flow area. The bellmouth would have brought the efficiency of the throttle body up, just like the pipework does, just with no filter reducing flow. Sounded cool too you can properly hear the charger.
Bell mouth test setup This is in engine hp. The peak 278hp figure is with bell mouth (blue line) red line is with filter and netted about 268hp. For ref the engine hp figure from last year, with filter was 283hp Fainter trace is with bellmouth. You can see MAP is significantly increased indicating a volumetric / mass flow rate through the supercharger.
What kind of dyno was your previous run on? Dyno Dynamics are known to often read lower than others. Some say you should add 15-17% to a DD number to get an equivalent Dynojet result.
In general, dyno numbers can be somewhat of a crapshoot unless using the same dyno to compare cars or modifications. I wouldn't sweat the lower number unless you suspect something is wrong.
What kind of dyno was your previous run on? Dyno Dynamics are known to often read lower than others. Some say you should add 15-17% to a DD number to get an equivalent Dynojet result.
In general, dyno numbers can be somewhat of a crapshoot unless using the same dyno to compare cars or modifications. I wouldn't sweat the lower number unless you suspect something is wrong.
Previous dyno was a Bosch FLA eddy current.
Yeah I guess that's the thing. Everything seems ok (apart from the WI that needs some attention). Car pulls well, no smoke, no misfire, no venting of block, good comp and leak down but I can feel it isn't as fast as previously. I don't know whether its just a combination of lower comp and stock cams with a particularly harsh dyno, or if there is something else going on.
I have noticed that I was only making up to 192kPa yesterday with the filter on, and previously on the road in similar weathers and the same cam timing I have been making 200kPa at the same revs, so I will take a look at the bypass valve to make sure that all looks ok. It might also just need a couple of degrees timing, but my testing on the road hasn't been sensitive enough to pick this up.
My plan is to get the car back on the original dyno sometime before xmas, as this seems to be the best way to truly compare.
Hmm, I think the DD is also an eddy current dyno so you may at least be in the ballpark with the readings. If you can tell the car feels different, that's also an indication that the numbers are closer to reality. When I tuned my car 12 years ago I just looked at AFR and listened for ping to see that I was safe. You're making a lot more power than I am though and you have more variables under your control.
Boost readings can also be a red herring since that's just a measure of pressure, not airflow. I haven't read your whole thread, but I did see you'd done some port work to improve airflow, and that can reduce pressure by reducing restriction and letting more air into the engine (a good thing). Not telling you anything you don't already know. Same with lowering the charge temperature with water or an intercooler and seeing a lower boost reading, but potentially making more power by being able to add timing back in or run a more optimal mixture.
Good idea to check the bypass though. I remember my bypass started to leak not long after I installed my SC and boost dropped significantly and the blower sounded like **** at idle.
Boost readings can also be a red herring since that's just a measure of pressure, not airflow. I haven't read your whole thread, but I did see you'd done some port work to improve airflow, and that can reduce pressure by reducing restriction and letting more air into the engine (a good thing). Not telling you anything you don't already know. Same with lowering the charge temperature with water or an intercooler and seeing a lower boost reading, but potentially making more power by being able to add timing back in or run a more optimal mixture.
Good idea to check the bypass though. I remember my bypass started to leak not long after I installed my SC and boost dropped significantly and the blower sounded like **** at idle.
Yeah it was more just an easy comparison rather than an absolute if that make sense. I know what the boost curve looked like with this head / cam position at WOT a couple of weeks back in similar weather, and the normal shifts I see due to weather changes aren't usually that large. I think there was one morning last year that was really very cold when I went logging and it gave me an extra psi. This is about around a psi down but in the same mild weather we've been having the last few weeks.
It could be bypass, it could be something dumb like the throttle isn't opening all the way. I'll run through all the obvious stuff.
The weird thing is the stock head is actually calling for more fuel across the board, suggesting greater airflow, yet it doesn't feel as fast or dyno as well. Weird.
I've checked the throttle opens all the way mechanically and it does.
I need to see if I can get the whp figures off the dyno guys on Monday, but doing a rough comparison shows I am down on torque at the wheels right across the rev range. Its not just a top end thing.
Looked in the logs for any knock retardation n and there wasn't.
Checked mechanically the trigger offset is correct in the tune and it is atleast roughly. My timing light is playing up so need to sort that and check the fine tuning. I'm not dismissing it could be timing but the trigger wheel / mk2 crank sensor setup because I haven't had the strobe on it, but it doesn't really allow any slip or adjustment mechanically.
Still need to check the bypass because of the small boost drop, but the car has felt slower since I put the rebuilt engine in. I also don't think a 5% drop in kPa would net a 15% drop in torque.
Comp tested as really healthy at basically 15bar across them all. I don't see how only a 0.5CR drop from my last head to the stock head would result in the 15% drop in torque.
Need to check the rear brakes but I would expect to not be able to push the car around / smell them if they were binding to this extent.
No nasty noises from the gearbox, more nasty noises than usual from the diff.
Wahey! I seem to have got the water injection running properly again. Lines look normal (not full of air) and it is properly proportioning. I just cleaned and rebuilt all the nozzles and made a little tester that comprised of a syringe and a pressure gauge so I could see the check valve was only opening at 13-14psi like it should and that flow could not reverse through the nozzle. Seems to have worked so far.
I'm going to try running the car on some mineral oil for a little bit, on recommendation of my tuner Dale. Hopefully if the lack of power is because the rings aren't broken in enough this will sort it before the next dyno session back at his in December. They didn't have the best ride to start, with the no comp head issue and me rushing around before the trackday before then putting full synth in it probably earlier than I should and then blowing it up. numpty. I wonder if at low pressure and low speed (comp test and leak down) they are ok, but then aren't properly seated during high pressure / speed operation, maybe.
Also on the dyno in December if it is a drivetrain drag issue it should show itself, because this dyno uses a coast down to calculate drivetrain losses, and this calculation will be consistent with last time I went. If I see a massive difference in losses this time round it could point to something.
I've been chipping away at the head, and it is getting there. The valve guides arrived, Supertech bronze intake guides for the Mx5, but the shorted Subaru EJ25 intake variant for the exhaust, to allow the raised port roof on the exhaust side - as per Na8cgee.
I'm not going to be fitting the guides or cutting the seats myself, I'm putting it into a one of two machine shops that I know will do a good job. I'm selling the Neway's to cover most of the cost of this. As much as I would like to become my own machine shop in my garage, I'm just not. I want the head to be bang on and I have realised my limitations.
In good news it looks like my car is going to be featured in a magazine here in the UK. A photographer for it asked me if I would be interested in it after seeing the car at a show a little while back. I didn't hear anything for quite a while after so had forgotten about it. Got a text out the blue and it was arranged. We found a good setting and it was a lot of fun getting the shots and doing the interview. I've not had a car featured or done anything like that before so it was a lot of fun. I will share some of the photos when I can after the mag comes out in beginning of December.
In sad news I found out that Dennis Priddle, who had helped so much in the early stages of the project, sadly passed away in April this year. He hadn't emailed back over the summer, but I wasn't going to chase him about it. I was fact checking a couple of bits for my interview and sadly came across the news. RIP Dennis and thankyou for all your help.
Had a bit of an odd issue with the car last night. I turned the ignition switch off, the engine stopped but the fan came on and the AFR gauge stayed on. I know the fan can come on if the car is powered up without the ECU being on - but the AFR gauge takes its power from the same line as the ECU. When I investigated with my multimeter the 12v line for my ECU etc (red/white fuel injection 12v) was hanging at about 2v after the ignition switch was switched off. I thought first the fuel injection relay, but I swapped in another 2nd hand relay and the problem persisted. I then thought it must be the ignition switch itself, but when I checked other items that need the ignition switch to be on, but aren't powered from the fuel injection 12v line (wipers), they turned on and off as they should. So I thought I might have a short somewhere, but I noticed when I tapped the fuse box it turned everything off properly. Long story short it turns out that both the fuel injection relays where dud.
I have ordered a new, first hand relay. This is the 2nd / 3rd relay including the spare that has gone in the last 12months. Doing a bit of research issues with this relay seem to be quite commonplace, particularly when running a larger fuel pump and a higher fuel pressure, which I am.
So I spent today adding another relay for the fuel pump, with its main high amp feed coming straight from the battery. So now the fuel injection relay only has to deal with the current to switch the relay with regards to the fuel pump, rather than the full pump amperage. Hopefully this will stop any future failures.
Interestingly after I did this the car started up really eagerly. I have been struggling a bit with cold start recently. Figured it was just a tuning issue and was going through the motions to correct. Early days but I wonder if the fuel pump wiring was part of the problem, either through some aging connections or simply now creating a separate path for a reasonable proportion of the total current required during start up to flow. I'll keep my eye on it.
Got a trackday next week, so hopefully that all goes well.
Had a good trackday yesterday at Donington Park. The track is a 'full size' track, pretty quick with decent straights.
Weather was great, no rain, just above 10degC temps.
First up I'm not going to be picking bits of bearing out the oil pan this weekend.
I put 0.2 litres of oil in it at midday, and arrived back at home with a full sump. For the laps we did and the nature of the track I am very happy with that. The car had the oil my tuner recommended for de glazing in it yesterday, so if there was any break in issue that can be fixed externally by this I would think yesterday would have done the trick.
The water injection worked faultlessly all day, and I can see in the logs it was metering correctly.
I was sharing driving with a friend, so the car had a passenger (and the weight) in it all day but it felt like it was pulling well, a lot better than anglesey, where I was running with incorrect cam settings / an about to go rod bearing.
Manifold pressure was up to 200kPa by 7krpm, vs 190ish on the dyno. Interestingly when I compared atmospheric pressures yesterday they were quite high about 101kPa, vs mid 97kPa on the dyno day, which goes someway to explaining the difference.
Basically it didn't feel down on power yesterday (despite passenger weight), oil usage is in check and when my friend drove the car and I watched it down the straight there was no smoke. So to me this does not suggest there is an issue with the bottom end, which is good, or perhaps the magic oil has done it's thing. We'll see on the dyno I guess.
I was interested in seeing what the air charge temps were like, as the track is fast with quite a lot of continuous time on throttle. The log below shows a short straight up a hill in 4th, round a right hander then a straight going through 4th up into 5th, down two gears for a quick chicane then the start finish straight going through 3rd, 4th then 5th. It was taken from a lap towards the end of a session. Those used to big a/a intercooler may laugh - but I am pretty happy with this. Peaking at 48degC, but basically under control oscillating around in the mid 40s.ambient conditions as above.
I've got some on track videos which I will upload in time.
I think really the only very slight disappointment was the higher speed corners showed up the limitations of the ad08rs tyres. Just felt a little vague after a few laps as the heat got to them. That said they got me to the track on a cold dewy morning across country roads with confidence and without any hint of drama.
I think next year I am going to get a spare set of wheels, so I can run a more focussed track tyre for my summer track days, but I have a fall back for the winter if the weather doesn't look good.
Got another trackday on the 27th of this month, hopefully that goes just as well.
Trackday went well in the end today, albiet not with the most promising start. There has been a storm going on in the UK, and weather was not fantastic. Luckily just wind and rain where I was though rather than snow.
Got to the track after a pretty tricky and grim country drive in the dark to find one of my rear tyres had a puncture. Luckily it was only a very small hole, from a thorn or nail, that I was able to get repaired at a local garage.
Conditions were difficult all day, wet and very cold so quite a challenge on my tyres, not a lot of grip particularly on the faster corners and braking zones that get rubbered in in the dry, then become ice rinks in the wet. Basically there was no middle ground on most corners, you were either understeering or oversteering, but we had fun, can ran well and did the whole trip with minimal oil usage again. It was also a very limited numbers day, so minimal time was spent up the bumper of the car in front which was nice, and a bit of a change.
The magazine article came out. I was happy about it and it was good to remember the story of the car pre Autorotor too. Here are some of my fave pics from the shoot a month or so back.
Been having an annoying issue on the car currently, where it is fuelling a point or so rich of where it should be, but not consistently. The AFR sensor had a bit of a flap at the beginning of the drive home from the last trackday. It read full rich for a short period of time, then did its full lean fault, but then returned back to normal.
I've checked the tune, corrections etc and there isn't anything that would cause it. I've driven the car in cold weather with this map again without issue. In the logs there isn't anything that would indicate increased fuelling (injector pulse widths). I drove the car to a meet on Sunday, It behaved itself all the way, then I gave it a bit of a squirt up the final mountain pass to get to the meet and the sensor through a wobbly again.
I'm going to replace the sensor (again) to see if that changes anything. It does need a bit of a tune, because I don't think my injector dead times and voltage correction is correct. Because of rewiring the fuel pump it has given the ECU a little more voltage, about 0.5v increase. With my current settings this voltage increase would cause the car to run a little richer, because the dead times in reality are shorter than the ECU thinks. I'll see how I get on.
One thing I have noticed is the car does use a bit of oil. Nowhere as bad as it used to bit still a bit. Its more noticable now because I have actually been getting quite a few miles on the car. I estimate its about 1litre per 1000miles. Also the catch can seems to fill a little quicker, although it might be the weather, with the additional moisture in the air and the cold weather making the vapour more likely to condensate in the can.
Dyno on Friday so we shall see if the power is back up, either due to dyno or magic oil.
Hopefully we get back to 250 or so whp. I think if we are still significantly under that I will be pulling the engine and re ringing it, as I think it indicates I ballsed up the break in.
In other changes I have decided not to go all out on the cylinder head. My plan is to pull my current head after xmas and give it a bowl and SSR job, then skim it to up the comp. This will be in tandem with the re ring dependant on the dyno results. I'll get it back up and running on the stock cams, but take the shim measurements to be able to swap back to my bigger cams later on.
So this will keep me at standard valve sizes on the exhaust, but I've woken up a bit and realised the extra work and machining to do the +1 ex valves with the raised exhaust port roof was going to cost me £6-700 for 3hp at 7krpm. More like 8hp at 8krpm, but a dose of realism tells me that I just won't operate the car up that high. It also means if I have an issue with the engine in the future and the head is damaged it isn't such a massive expensive PITA to sort.
It lets me fix the rings if required, get most of the headwork gains and do the airbox / filter improvements without costs spiralling.
Good news from the dyno! So if it was rings and bore break in it is sorted, power is back on track.
The car made 255whp / 287hp and 245lbft. Peak torque was quite a bit higher, up about 20lbft from last year. This was a bit of a surprise, my simulation predicted a smaller peak tq increase due to the smaller stock intake cam in the stock head.
I then tested out my new big filter from ITG. It is their Mega Maxogen, but they did me a 3" spinning for my intake pipework. It is about twice the filter area of my current filter. You can see the reduction in intake vacuum and increase in boost pressure this gave in the graph below. This boosted power to 264whp / 295hp and 246lbft. The gains are up top of the rev range as you would expect as air flow increases. Decent gain at the top of about 10hp. Just need to try to fit the thing in the car now, and build the air box for it.
We then put a couple of degrees timing and I was actually surprised to see a decent gain, so in the end 268.5whp / 302.3hp and 251lbft. This is all without the water injection on, just on petrol.
So it went to plan. Really the surprise is the peak torque. I'm not sure if this is all down to the smaller intake cam or if I would still see the majority of the increase with my big cam, but with the bigger top end. The sim reckoned there was about 3lbft @5krpm between them. Need to analyse the numbers some more. One thing we did differently was actually plugged the tach output of the car into the dyno, so it could calculate torque. Last time I calculated torque from the wheelspeed and whp.
10-14-2021, 07:16 PM
0
you can properly hear the charger.
numpty. I wonder if at low pressure and low speed (comp test and leak down) they are ok, but then aren't properly seated during high pressure / speed operation, maybe.
