Zed.

the brass plugs are common to several engines iirc, as to blocking the drillings - thats a good thing to check but you can use a long-series dril to clearance the brass if its overlapping slightly?

got a link or item number (I'm lazy)

cheap insurance.....

sorta what I'm doing, will keep you posted with the dims & (if you've not sorted something by then?) make you one...

Rich.

Tchaps

My issue was that to fit the threaded plug I needed to spoil the surface the stock plug would sit and seal in. If it didn't go well then I'm up there without a paddle. Also on the rear of the block the casting necks down after the plug and I was worried about going through the wall. When I saw the stock plugs were available cheaply from Autolink it was a no brainer really.

Yep, but it seems to be the only one avaiilable https://www.ebay.co.uk/itm/324497626...iABEgLjzPD_BwE

I would have thought a Mazda dealer would stock it though.

That would be greatly appreciated do you need the orifice diameter? I saw in your thread you drilled it out before measuring.

I do also have my scrap block that I could angle grinder / punch it out of, but I don't like reusing interference fit things. I measured the diameter of the galley plugs I took out vs the new yet to be installed galley plugs and there is 0.03mm difference in diameter between them. I don't want an old restrictor floating around the engine when its warm. Could also remake them by drilling an allen brass plug, then tapping the block for a nice reusable restrictor.

Zed.

I remembered a thread (that I'd commented on / killed) where GC threadded the block for removable screw-in plugs...



https://www.miataturbo.net/general-m...removal-95289/

obviously if the plug is slightly proud then the bellhousing & oilpump / front cover could be trimmed to create the clearance?

this other thread has some other usefull info

https://www.miataturbo.net/engine-pe...oil-pan-98997/


looks like Mazda or possibly engine remanufacturers used coreplugs (freezeplugs?) in place of the brass item but theres a nice image with p/numbers for future reference..

Rich.

Tchaps

Thanks for the links. I think if I was going to move away from the OEM plug, or an exact copy of it I would feel more comfortable with a screw in, and then shorten the back end of it to suit and not interfere with anything.

I looked at those core plugs but I was a little shy of them, didn't know how tight they were going to fit, didn't want to find out the wrong way.

Got my engineering straight edge and I've done a very quick mains alignment check and it all looks good. I'll get some pics when I do the full check this weekend.

Zed.

bolt & torque the head & main bearing caps before checking, it’s possible that the assembly can move slightly (for better or worse?) adds a few extra mins but you get the actual structure not just the block…

iirc, I built a Volvo b230 engine ~20 years ago and the crankshaft wouldn’t turn without all main caps fitted & tightened🤔



Rich.

Tchaps

Yes I was / am going to fully torque the mains with lube as per normal assy when I do the proper measures.

You've guilt tripped me into doing it with the head on now. May as well.

This will still be a pretty rough check anyway. The standard of my straight edge is a maximum deviation of 21microns over the 500mm length.

Sounds like naff all but the reality is that is the best part of a thou - or half the oil clearance. Also the thinnest feeler gauge I have is about 1 thou, so the test is fairly crude.

I will check for concentricity twice for each position around the mains circumference, one for each side of the straight edge to make sure any gap is the same both times, which would indicate the main being out rather than the straight edge

Tchaps

Ah *****.

Got the oil restrictor out and it doesn't look the same as the one I ordered.

But of digging and the part for the Mx5 / Miata is B366-10-305 not the RF01-10-305-A I have ordered. Doesn't seem to be an easy source in the UK.

Good thing is it seems to be a very simple part. 8.5mm diameter, 7.5mm long. Orifice 2.5mm, maybe slightly under like 2.45mm. I think it's stainless steel. Its silver in colour, not magnetic and its not aluminium.

Plan is to tap the block for 1/8npt, then drill out an allen plug to 2.3mm and screw that in. I'm thinking slightly smaller than stock because the hole will be slightly shorter than the stock plug and so possibly slightly less restrictive a​​​​​​​t the same orifice size.

I just feel a bit nervous cutting a plug out of my scrap block in a wa​​​​​​​y I could reuse it - if it refits slightly looser it could just float off into the head oil galleries. Maybe I'm being over cautious.

Tchaps

So I went to fit the oil pump on to the new crank I bought and oddly the nose of the crank was too small in diameter to drive the pump or for the seal.

Really odd because I thought 1.8 cranks were created equal. I didn't even think to measure the oil pump drive area because of this.

I'll look what the casting mark on it is before I send it back.

So I ended up using my spare crank I already had. I've set it up with 2 to 2.2thou clearance on mains and about 2thou on rods. This should be nicely setup for 10w50 at my normal oil temps, and also matches the 50wt oil requirement for the supercharger nicely. I have enjoyed measuring it all and matching up the bearings etc to equalise clearances. Whether I reap any particular power benefit from it I doubt but it gives me satisfaction. Hopefully I got all the shrapnel out of it this time.

I made my new head oil restrictor out of an allen plug, with a 2.3mm hole drilled through it. Sits nice and under flush with the deck, and is removable and replaceable if I need to later down the line.

Got the engine all back in the car and the supercharger stuff back on. I changed some of the fittings on the water injection manifold from straight compression to 90deg swivel compression. The previous setup made it a real pain to get at the injectors or remove the supercharger setup, you had to force the pipes out the way and work under them and I was conscious of stressing out the fittings or pipes. The new fittings can be removed easily from the manifold with a screwdriver without having to touch the compression parts. Should be a lot easier to work on. It also helps the pipework out by meaning they don't have to make such a tight turn straight out the manifold as the fittings can swivel more towards the nozzle in the first place.


Gave the nozzles a clean while I was at it too.

Got the car fired up, all seems well on the engine front, although the throttle body was whistling again but I'll sort that out easy enough. Great oil pressure, fired right up, starts nice and easy, revs up nice.

Only issue really is the chargecooler pump sounded a little off when I was first priming the system, and low and behold a few priming pulses later it ground to a halt. Pretty annoyed to be honest, its just over a year old and it's not like I've put massive miles on the car. I got it out the car and the motor felt rough as anything when I turned it by hand. I separated the pump head and that spins freely, no evidence of it eating anything. Relay appears to work fine, fuse is also fine. I've ordered just the same pump again to replace it quick, as there is a few events I want to get to, but I am going to look at other options pump wise, like possible a small Davies Craig electric water pump for next year. I will also take another look at how I have it wired. I run the pump flat out all the time the engine is running, it is wired up to the fuel pump relay output on my Megasquirt. I don't really see the point in PWM controlling it because I always want temps to be as cool as possible. I am conscious I don't have a fly back diode in the wiring for it though that may possibly be a contributor. Might look at relay options that incorporate some protection.

Anyway should be able to sort it in the next couple of days then I have a couple of shows to go through this weekend and next weekend.

Once the car is on the road and running well I am going to go back and look at that cylinder head that had no comp. My moneys on a shoddy valve job by yours truly but we shall see. Likely that I need some more practice with those Neway cutters. Then I am going to start putting together the upgraded cylinder head over the next few months.

I think I am going to also go with +1 intake valves to maximise intake flow. Something Ted said a while back on fb highlighted an advantage to a better flowing head I hadn't previously considered, that for a given charger rpm air flow is slightly lower at a higher pressure ratio. i.e lower the boost pressure through a better flowing head and the supercharger should move more air and produce more power. It is why the rpm lines on a supercharger efficiency graph move rearwards as pressure ratio increases, see this Sprintex graph that should be roughly equivalent to my Autorotor.

My supercharger should be flowing about 205l/s by my calculations, at a PR of 2. If I managed to get the same pulley ratio to achieve a PR of only 1.8 by increasing the flow through the engine the same rpm line should net about 210l/s at this lower PR.

Really roughly if air flow is increasing by 2.5% then I should expect to see a 2.5% power increase - or about 7.5hp.

If you couple this with the expected gains from a lower power requirement to drive the sc aswell as some of the other ramblings from way back in my thread before I started breaking everything then we could be looking at a decent 10-15hp boost in power, which I don't think would be too shabby. Gives me something to play over the winter anyway.

Tchaps

Wahey! I've driven it 20miles!

Swapping out the chargecooler pump was not the massive PITA I expected, it went quite smoothly. I remember the pipes being very hard to push onto the pump originally, but obviously time and the fact I am refitting them meant they came off and onto the new pump with a medium amount of persuasion.

Engine fires up hot and cold nice and easily. Oil pressure is good, builds nicely with revs. Its not banging up against max pressure by 2500rpm anymore, and pressure is nice and stable on the brakes too, the couple of times I gave them a hard stab. No nasty noises from the head so far so would seem so far my 2.3mm oil restrictor is enough. I'll do a few more miles then get the valve cover off and double check the cam lobes and journals.

Only issue is the whistling under vacuum. Needs more investigation but its not a vacuum line and there aren't any driveability issues. Sounds like it is coming from the throttle body. I'll use my leak down tester to pressurise the intake and see what I find.

I'm also going to double check out the cam positioning against where I think they are - I'm pulling a lot of vacuum at idle which could be that I inadvertently have the intake too far advanced, and would also explain the slight feeling of urge in the upper rpms when compared to my upgraded cammed head.

Was great to see it out in the sun again today, I've really missed driving it over the summer.

Tchaps

Had a pretty good weekend with the car.

I made it to the car show, although annoyingly there does seem to be a couple of issues.

The most annoying is that the AFR gauge occasionally read full lean for no particular reason, at times I know it is not full lean. No stumbling etc, drove normally so it is something up with the sensor I think. I watched it carefully and there wasn't any particular consistent situation that the issue happened. I think the sensor has gone bad. I think its about 3 years old so its not had a bad run, just the timing is a little frustrating.

The idle air valve also seems to have an issue. It was hard to start cold (not slow cranking, just was harder for it to catch and it was struggling to idle. Giving it a little throttle solved it and the engine sounded well. I plugged in the laptop and adjustments to the valve duty in the map made no difference to idle rpms. I've got a good 2nd hand valve coming to try, if that doesn't work I'll look at the wiring and the transistor in the ECU. Again, nothing to horrible to deal with but annoying.

On a good note no oil was used in about 150miles round trip, no smoke, no knocking and when I had the valve cover off this morning all looked well in the head, so that is a success. On the way back I also met a BMW i8, it was interesting that he had the low end legs but then as I got up into the 5000+rpms I would reel him in. The car still felt a little flat though.

I checked the cam timing early this morning and although the exhaust cam was where I thought I had put it, the intake was 7deg retarded - 117ATDC full lift. I actually thought because of the fueling differences I've seen between heads / cams that I had it too far advanced. Either way it was significantly off and will hopefully bring a little bit of urge back that I have been missing.

I also upped water injection % to max for my previous trackday and I wonder if I am now overspraying a bit, so I will experiment again with that.

Anyway, it was nice to use the car again, even if there were a couple of small niggles.

Spaceman Spiff

Glad to hear it's back on the road A-OK! Your build cadence always amazes...out here embarrassing me out of build paralysis 🤣.

So are your water injection locations just in the runner for each intake? Little hard to tell from the pictures and as I piece together my own setup I'm debating just using some less-than-ideal existing tapped holes.

Tchaps

Ha ha thanks, It's usually because I have arranged a trackday / meet in what I think is plenty of time, engage scope creep, have problems, rush around stressed out, just about get it together, blow it up, take it apart, repeat I don't recommend it.

The improved cylinder head is going to take a more relaxed pace.

Yes they are just in front of the injectors, in each runner of the manifold. They are leaned back to spray down the port and also more convenient for the water supply pipes.

Tchaps

I fixed the whistle, it was the actual throttle plate itself. Because I fixed the idle air valve (broken wire in the plug) I could close the plate a little more and it stopped. Must just be that rpm / air requirement at idle and that throttle opening produces some sort of harmonic. I've had weirder stuff go on.

New lambda sensor sorted out the random full lean AFR readings.

Had trouble with a misfire for the millionth time. I wiggle on the HT lead to coil pack plug solved it this time but it just doesn't seem to be a robust system. I've had enough, it happens too often and really annoys me. I'm moving to the VAG black COPs to take a failure point out of the system. The VAG coils are plentiful and cheap over here, and easy to keep a spare in the car and swap over only by hand if I did have one go.

Correcting the intake cam timing has certainly had a good effect. I had to add a load of fuel back into the WOT parts of the map, back to equal the WOT fueling requirement of my modified head. This also translated into the WOT urge returning. Very happy about this.

Tchaps

Carrying on the thinking regarding power increase from reducing pressure ratio by increasing cylinder head flow.

I wanted to run some numbers on how the drive requirement would be increased by the small increase in volumetric efficiency of the supercharger (and therefore volumetric flow rate and mass flow rate) by lowering the PR across it. I thought this drive requirement increase might mitigate any gain from the increase in volumetric efficiency.

It does reduce the reduction in drive requirement from reducing PR, but by a small amount that doesn't cancel the gain. I calculated that if the PR was reduced from 2 to 1.8, but the flow rate remained constant then the gain seen was about 0.7hp more than when the same calc was run but flow rate increased by 5litres per second at the 1.8PR

Then I calculated the expected gains from achieving a PR of 1.9, then 2, with the estimated increase in litres per second at those PRs (2.5, 5 respectively).

See attachment but basically roughly there is a gain of just over 6hp per 0.1PR dropped. So if the cylinder head was modified to produce a PR of 1.8 at this pulley ratio I gain 12-13hp. This gain was pretty consistent at the flow rates I expect my supercharger produces between 15 and 19krpm.

It assumes a few things. That the relationship between volumetric flow rate of the supercharger and power is linear, that the isentropic efficiency of the supercharger remains constant within this relatively small island we are working in, that inlet temperatures remain the same and that the induction system can supply the small increase in air flow without any additional pressure drop in the intake.

I think the other thing to bare in mind is that if you dramatically altered cam profile or timing to achieve the PR drop (by increasing overlap) then I think it is unlikely the supercharger flow to power conversion relationship would be completely linear.


Anyway may turn out to be a load of rubbish but I think there is a reasonable case for pursuing a better flowing head.

This also doesn't take into account any gains that can be made in the exhaust port, or a small increase in CR.

Ted75zcar

iTrader: (2)

Fold density ratio into your analysis and you will get even more excited

Tchaps

Oooo care to elaborate?

I thought calculating from a predefined pressure ratio simplified what for me atleast was a pretty complicated calculation of flow rates, pre and post expected chargecooler air temps and densities

Ted75zcar

iTrader: (2)

Well if you are doing charge cooler outlet density, then you are probably already doing density ratio whether you were aware of it or not. In short, SC efficiencies are a function of Pressure Ratio, and HP considerations operate on Density Ratio. This isn't specific to SCs, it applies to any compressor, but SCs typically show a larger discrepancy between the two numbers due to a reduced thermal efficiency. Take what you read on the internets with a grain of salt (including what I say ). You will find some that say charge cooling doesn't increase HP for SCs beyond detonation resistance. An example given relates to a balloon, where the inlet volume of the SC is used to fill the balloon, and the mass of air in the balloon is not a function of the air temperature. This is in-fact a true statement. What is left out of that conversation is that if you decrease the temperature of the air already in the balloon, the air gets smaller and the balloon shrinks. The ICE air pump is volumetric, so it consumes a fixed volume, not mass. This is why we see a reduction in PR with an intercooled system. The engine is consuming more air mass, it makes the engine look "bigger" to the SC and reduces the pressure ratio. Now we get back to the Pressure ratio, which is what causes SC VE to drop and SC drive HP to increase.

You are getting into the details now with your analysis, the impact of these little things isn't great, but it is fun (for me at least)!

Tchaps

Ah yes got you, just hadn't used the terminology density ratio before.

I did some calcs a while back and I think my setup would run at about 19psi / 2.3PR unintercooled, assuming the same supercharger volumetric efficiency (which I now realise is incorrect)

It's this increase in volumetric efficiency, and lower drive requirement I want to exploit.

Ha ha I'm more interested in eeking 12hp from this setup with careful optimisation and a large vacuum cleaner than moving to a bigger supercharger and making another 100hp if I'm honest

If I was starting from scratch on the head it don't really think it would be cost effective but I already have the parts really (this is my excuse) and if I can bag another 10-15hp out of this setup just with some optimisations I will be really happy.

Tchaps

So I have started collecting parts to build a flow bench. Bought the PTS flow bench plans on recommendation of Warpspeed, because as long as I build it correctly I know it is going to work and be repeatable.

I have got 3x 1400W vacuum cleaner motors. That should (I think) be able to pull 300CFM @ 44" (28" test pressure, 16" depression through orifice). I can add another if they need a bit of help. That is about the limit of current draw I can / want to run off a single ring main.

I also downloaded Lotus Engineering Engine Simulator. It's free to download and use. The intention is to build a model of my setup with the aim of being able to assess changes in port and cam design virtually. Obviously that is far easier and cheaper than doing it in the metal.

I'm chipping away at it, but it is one of those bits of software that makes you realise truly how little you know. It is a great education though, if a little frustrating. I have made a model of the NA mx5 engine, in the hope of being able to achieve the stock power / torque curve as a benchmark, then add the supercharger and benchmark again. Once I have got that sorted I will feel relatively confident that the model will honestly assess changes. The torque curve it incorrect at the moment, so it needs some more work. I did also do a quick supercharger add on just to test and it came at just over 300hp, which is about right, but again the torque curve needs some work.




It seems to really love big dirty cams, which although my heart loves, I just don't quite believe yet and is probably the result of not having something set up right.

HarryB

Engine Sim is a decent tool; the FSAE team has been using that with success before transitioning to Ricardo Wave back in 2007-8. How did you manage to get a free version for a 4-cyl though? Last time I checked the free version supported only 1-cyl models. I believe you will need to add a 2nd intake valve, exhaust valve, and runners to each cylinder, before joining at the plenum. I think you also need a throttle element on the intake side. You can also add all exhaust elements (mufflers, bends etc).