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I'm glad you looked that up because these two statements above don't correlate unless you have an eighty or ninety something millimeter exducer. That would be a big turbo on our cars.
That would take a high rpm manly man build of a mazda bp to use a compressor wheel with a 90mm exducer LOL.
My current churbo is 58/76 on the compressor and 68/62 on turbine with an .82ar housing and that is one lazy sob...... If it wasnt for my spool shot it would be a real pig on the street.
I did try a gt3582 churbo with a .63ar briefly. That turbo used a 61/82 compressor wheel combined with the same tubine wheel as above. It surged the compressor badly at anything below about 5300rpm in higher boost.
I'm glad you looked that up because these two statements above don't correlate unless you have an eighty or ninety something millimeter exducer. That would be a big turbo on our cars.
A sixty something millimeter exducer will typically be matched to a forty or fifty something millimeter inducer. On our cars that is not considered a big turbo.
An interesting point that was not mentioned originally when you said you installed a new clutch.
On RX7 460cc injectors a well tuned car can go over 200whp at 85% duty cycle on a log manifold and stock NA8 head. Your head breathes better. What deadtimes are you using? What AFR are you targeting?
Virtual dyno is incredibly unreliable so I wouldn't use that as a real measure against numbers other cars are putting down on actual dynos. Just like you can't even begin to compare results from two different cars on two different dynos. The same Miata can be different by 50 horsepower on two dynos (especially in western Colorado). Virtual dyno is only useful for tuning against its own data.
Did you account for the larger diameter of those rear tires in virtual dyno?
Forgot my Micrometer at work. Quick tape measure puts me at 60.38mm inducer and 76.2mm exducer on the compressor.
Forgot my Micrometer at work. Quick tape measure puts me at 60.38mm inducer and 76.2mm exducer on the compressor.
Using 1.2 deadtime and 11.5 afr at 13psi
Thats a pretty big compressor wheel for a 1.8l engine That doesn't rev over 7000 rpm. Thats a 650hp compressor wheel. Whats your turbine wheel size and exhaust housing ar ratio? Im wondering if its a 60/48 turbine wheel. That would make it seem to be a turbonetics tnx30 turbo. Which in my unprofessional opinion is a poor compressor to turbine match to begin with. If it has an exhaust housing ar small enough to spin that compressor wheel to full boost anything below 5000 rpm youve got to be to the left of the surge line on the compressor map below 5500 rpm and choking exhaust flow at high rpms with poor flowing turbine side. Again just my amateur guess. When you can measure that turbine wheel and find the housing ar number. Also might want to show your timing map.
I know that this turbo is far from ideal for this engine. But the car still gets fantastic fuel milage and I've never had a surging problem. The end goal is to have a turbo this size on a better bottom end with a ported head and maybe even different cams to drag race with in the 4-500 hp range. I figured for now I could get the car to 250ish whp and play with it while I hunt an engine to build. I dont mind that it is peaky and has a very small power window because I know the is not the engine I will run best with. But for the car to on do a 96mph 1/4 on 13 psi is not adding up for me. I just pulled the spark plugs and they look caked up. I may have put colder plugs in sooner than needed so they are not burning off residual contaminants. Will clean them up tomorrow and test again. I put some street tire back on the car for now. No reason for slicks on a 170hp car lol.
I know that this turbo is far from ideal for this engine. But the car still gets fantastic fuel milage and I've never had a surging problem. The end goal is to have a turbo this size on a better bottom end with a ported head and maybe even different cams to drag race with in the 4-500 hp range. I figured for now I could get the car to 250ish whp and play with it while I hunt an engine to build. I dont mind that it is peaky and has a very small power window because I know the is not the engine I will run best with. But for the car to on do a 96mph 1/4 on 13 psi is not adding up for me. I just pulled the spark plugs and they look caked up. I may have put colder plugs in sooner than needed so they are not burning off residual contaminants. Will clean them up tomorrow and test again. I put some street tire back on the car for now. No reason for slicks on a 170hp car lol.
Is that 60mm measurement the larger or smaller diameter of the turbine wheel? you didnt specify so I will assume its the smaller diameter. When I mention surging Im not referring to surging as something you can feel in the car,. Im referring to being to the left of the surge line in the compressor flow map. From measurements you sent it looks like you may be using a 60-1 20177t compressor wheel. If thats the case you are definitely to the left of the surge line (dotted line on compressor map) at anything below about 5200 rpm in boost. When running to left of the surge line the airflow out the compressor is unstable. You can get cavitation at the compressor blade tips and create excessive heat. I attached a compressor map so you can do your own calculations. What I dont understand is why you are falling off at 6500rpm if that 60mm measurement you mention is the smaller diameter of the turbine wheel. If that is the case that turbo should perform well between about 5900-8100 rpm range unless you have a problem elsewhere.
Is that 60mm measurement the larger or smaller diameter of the turbine wheel? you didnt specify so I will assume its the smaller diameter. When I mention surging Im not referring to surging as something you can feel in the car,. Im referring to being to the left of the surge line in the compressor flow map. From measurements you sent it looks like you may be using a 60-1 20177t compressor wheel. If thats the case you are definitely to the left of the surge line (dotted line on compressor map) at anything below about 5200 rpm in boost. When running to left of the surge line the airflow out the compressor is unstable. You can get cavitation at the compressor blade tips and create excessive heat. I attached a compressor map so you can do your own calculations. What I dont understand is why you are falling off at 6500rpm if that 60mm measurement you mention is the smaller diameter of the turbine wheel. If that is the case that turbo should perform well between about 5900-8100 rpm range unless you have a problem elsewhere.
Yes it is the small diameter. I'm not going to lie I've never looked at a compressor map and I dont quite understand it.
I figured that the engine is still limited by head and cam flow but I may also be having a spark issue as it gets higher. It makes boost all the way to 7500 just fine but the power falls off at 6500.
For now I am stepping back. I turned the car back down to 4 psi and pulled the spark plugs. Going to clean them up and play with the tune until I can get an even rise in hp and boost. I want 20% more air pressure to give me 20% more power and I'll slowly work back up to 13 psi hopefully with better results.
Timing belt been changed? If so make sure its not off a tooth or two. Thats easy mistake to make. Also make sure your vics is working. That helps higher rpm on 99 models. No way that turbo should fall on its face at 6500 without something else going on. Good luck with it and hope you get it ironed out. Would be good to see another miata on here into drag racing. When you get it ironed out I have a database on here im trying to get going labeled (post your 1/8th and 1/4 mile timeslips here please) for you to post your time and what it took to get there.
Have you been going to a track or using dragy or some other device?
I purchased this car with a blown up engine. I bought a good bottom end and rebuilt my head and put new timing belt on, on an engine stand. I can recheck timing if maybe it has slipped but I know it was perfect before.
I use the dragy. I didnt think that vics could work with megasquirt since I dont see any options to control it. I havent touched it.
Ok. power still falls off at around the same rpm, but with new spark plugs the car instantly gained a little power.
The only difference on these two runs were the spark plugs.
I tried tieing the VICS closed and it hurt performance.
The exhaust is currently a 2 inch pipe cut under the drivers seat. Tomorrow I am putting 3 Inch pipe all the way out. I'll let you guys know the difference then.
The exhaust is currently a 2 inch pipe cut under the drivers seat. Tomorrow I am putting 3 Inch pipe all the way out. I'll let you guys know the difference then.
Wait,,What?? Did you for real run a 2" exhaust on a turbo with a 60mm exducer on the turbine side? Yank that junk exhaust out yesterday. That is a detail you should have mentioned before. That turbo REQUIRES 3" minimum downpipe using turbine exducer x 1.25 formula. However 3" all the way back is also best for performance. You may want to send pics of your entire setup so people can see exactly what else could be an issue.
Also what der vierte said. Although it may lean out some when you get the exhaust right.
I've got a few things that I know for sure need to be fixed I'll get pictures of the whole setup sometime today.
I've got a short list of things but can only do so much at a time with 3 6 month old children at home.
When I assembled the car, mostly ebay parts, I bought a 2 inch intercooler piping kit. well my turbo, intercooler, and throttle body are all about 2.5 and I've got silocone adapters on each of the connections going from 2.5 to 2 inch pipe. the MAF is also still in place. After the exhaust, running new intercooler piping with 2.5" pipe is the next on my list.
I just leaned out the map. I'm going to make a pull on the way to the shop and make a pull after the exhaust is on to record the difference.
I've got a few things that I know for sure need to be fixed I'll get pictures of the whole setup sometime today.
I've got a short list of things but can only do so much at a time with 3 6 month old children at home.
When I assembled the car, mostly ebay parts, I bought a 2 inch intercooler piping kit. well my turbo, intercooler, and throttle body are all about 2.5 and I've got silocone adapters on each of the connections going from 2.5 to 2 inch pipe. the MAF is also still in place. After the exhaust, running new intercooler piping with 2.5" pipe is the next on my list.
I just leaned out the map. I'm going to make a pull on the way to the shop and make a pull after the exhaust is on to record the difference.
Nothing wrong with ebay intercooler and piping as long as you get the right one. Some ebay intercoolers are very good and some are restrictive junk. Since you didnt send a pic its hard to know what you have. Is your maf before or after turbo? If youre drawing through it you may want to switch to blow through. I run no maf.
Just to reiterate. When you redo your exhaust you are planning on 3" from turbo back? That turbo requires a 3" downpipe for at least the first tew feet off turbo. Would be best to run remainder 3" all the way back as well but if you reduce to 2.5 or 2.75 it may not hurt performance too badly. The downpipe size on a larger turbo is very important though. Follow the rule turbine wheel small side x 1.25 minimum and that puts you in the ballpark. You also need to take into account your catalytic converter and muffler. Those need to be very free flowing. If you are going to run a big boy turbo everything has to match its flow capabilities both on the exhaust and the intake side. For comparison my current turbine wheel exducer is 62mm and my exhaust is 3.5" from turbo back front half reduced to 3" rest of the way. My cold side is 2.5" all the way with a big intercooler and open turbo inlet with a 4" duct going to an opening i cut in bumper, although sometimes I do remove that and run a large open cone filter for street driving
I already had a 3 inch downpipe but it connected to the stock exhaust system later. I cut it at the transmission at some point and it picked up powe .
now we are running 3 inch from turbo all the way back.
Thats the exact same exhaust manifold I use. lol..
Now that youve got the bottleneck of exhaust removed you should see a much better topend charge when you go back up to 13psi provided your muffler and catalytic converter isnt too restrictive (if you run one that is) and your tune plus all else is right. Looks like you have at least many of the pieces in place to have a real mover when you get it right. If that is a 60-1 turbo you have it should support about 27psi boost pressure efficiently.
Thats the exact same exhaust manifold I use. lol..
Now that youve got the bottleneck of exhaust removed you should see a much better topend charge when you go back up to 13psi provided your muffler and catalytic converter isnt too restrictive (if you run one that is) and your tune plus all else is right. Looks like you have at least many of the pieces in place to have a real mover when you get it right. If that is a 60-1 turbo you have it should support about 27psi boost pressure efficiently.
Ok exhaust is done and at 3.6 psi I havent seen much difference. 136 tq@5215 and 152hp@6240
Power still falls after 6500rpm and I'm having some trouble leaning the mixture out. It was at 10.0-10.5 at high rpm and I've taken VE out twice taking 6-8% each time and I still have a 10.8 AFR at high rpm.
Could I have been so incredibly rich that I'm just getting to where the sensor will read?
I also think that my chinese wastegate is failing on me. It used to hold 4 psi with the MBC turned down now I am seeing 3.2-3.6
Werent you like 11.7ish afr when at 13psi? Have you tried to ramp back up to that level yet? At least you now know that you have an exhaust to support that turbo (provided cat and muffler free flowing) so that part is out of the equation. So now you can focus on tune, fueling and ignition.. Tuning will take some time learning, testing and logging. It will come together for you as you test and tune. If you can get the tune and all else right that thing should haul once you dial up some real boost with that turbo. Youll need to put those slicks back on once you get towards 20psi or more with that turbo and all your bugs worked out.
So you have baby triplets? how do you have time and money for a car hobby?
07-01-2020, 06:56 PM
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