power loss during race. heat soak??
 

my turbo race car loses power during a 20 min race. according to the data logs it is around 60-70bhp! i can only assume this is due to rising inlet temps but don't have the data from the ecu log. i have a good intercooler and ducting setup so what else can i do?? don't get me wrong the car still pulls well but just seems to lack a little. there is no sudden lack of power it is gradual thought the race and can be seen by comparing the power output in the logs from the start of the race to the end.

oil cooler covering too much intercooler perhaps?

considering water injection but only to keep the temps down and not advancing any timing for extra power. don't like the idea of melting my engine if the system fails. should make a little just from the lower temps but that's not the idea. just be happy to maintain the power i have for the whole race.

surely you some of you guys have the same issues if not worse with the hotter air temps you see.

https://www.miataturbo.net/attachmen...ine=1337680607

https://www.miataturbo.net/attachmen...ine=1337680607

Get a proper datalog from the ECU.

did do but when i copied it over i deleted it and it had not copied properly so i lost it. earlier logs show the inlet temps settling at around 52c but that was during testing and was not being driven quite so hard for so long.

Can you move the oil cooler to just behind the intercooler? That would definitely help.

not really any room for it there. think if i had to move it it would have to go somewhere completely different.

+1.

Until then, you're just guessing.
Your car looks serious, It'd be a shame to start changing things if you don't know 100% whats causing the power loss.

If your ecu is up to the task, you can have w/i activate only past a certain iat/map.

Check my build thread from the last page or so and look at my oil cooler set-up. Thank me later. Stacking heat exchangers simply does not work. Small, ducted heat exchangers...that works.

got some testing booked next week so will get a decent data log done then. in the logs i have, driving reasonably hard the inlet temps look fairly decent and stable at 52c. funny thing is the car did the same thing last year with a totally different engine, turbo, rad, intercooler, oil cooler, ducting and the list goes on... had a thought today that it could be the brakes binding slightly when they get hot so will have to check that too.

are there many race cars on here running WI?

I've run water injection on other cars. I'm sure the power loss is likely heat soak. I'm putting on water injection this weekend. at least in Nasa you need to get a waver from tech that says you told them and they looked at the system and it is safe. I think they just dont want you venting to air and or you must not run more then 50/50 mix.

well got a chance to get a decent data log of about 15 mins hard driving on track (before they kicked me off for being too loud, but that's another story all together) and the inlet temps slowly rose to 60C/140f. judging by the trend i think they would continue to rise too. also checked the ecu and it is set to start pulling timing from 50c/122f which would explain some of the power loss and cause raised egt's further increasing inlet temps meaning even more retard (chain reaction!). highly tempted to fit WI. first job is to move the intercooler off to the side and duct it (and possibly fan?) but with a race coming up soon i need to get this sorted.

what egts did you see? what race? I was informed recently that you need to inform NASA tech if you run WI to get a 'Waver" and I believe they prohibit straight meth and or require a bypass vale ( no blow off valve). dont know what your race is but just fyi, something to look into. obviously good reason for the rule, they dont want to see you burn your car up in an invisible ball of flames!

ha, just realized I said the same thing one post up, my bad

We race in the uk where I don't think there are such rules. Something to look into though.

Time to ditch the shitty eBay intercooler for something that actually works on track. The 600hp Precision core in Theseus keeps IATs to an absolute max of ~135*F in 100*F heat after two 100-140mph 5-6 pulls in a row. IATs reach 135*F peak on each pull, then drop as soon as I lift off the throttle. If I had even the slightest semblance of a cold air intake instead of an air filter basically sitting on the turbo, I'm sure I could knock 10 or 15 degrees off of that.

The intercooler is a quality item custom made for the car by forge motorsport here in the uk. Not saying it can't be that but it is pretty good. The oil cooler is blocking a lot of flow and feeding it hot air so first I am going to move that then see where we are. I know others are fine without wi. Just need to work out where I am going wrong. Be great to keep all 355hp to the end of a race.

I think IATs around 60C is high.

How air tight is your ducting, starting from the mouth of the bumper?
What are your water and oil temps?

ducting is pretty well sealed to the bumper but not air tight as the bumber is an easily removable part and comes off with the undertray. coolant temps peak around 100c and oil peaks around 120c.

have now moved the oil cooler off to the side and built a pox on the front to duct it with hoses. hopefully this will do the trick. if not... back to the drawing board.

few pics of the ducting i made for the oil cooler. not really happy with it as i dont think it will flow enough air through the cooler. didn't cost anything so it is worth a go. so hopefully should get a chance to give it a try soon. what do you think?? will it work?

https://www.miataturbo.net/attachmen...ine=1340473990
https://www.miataturbo.net/attachmen...ine=1340473990
https://www.miataturbo.net/attachmen...ine=1340473990
https://www.miataturbo.net/attachmen...ine=1340473990
https://www.miataturbo.net/attachmen...ine=1340473990

I like the idea. I was considering doing something very similar, except with larger hoses (left over 3" brake hose) and NACA ducts to feed the tubing. Ideally you want the inlet to be about 33% of the surface area of the heat exchanger. Its hard to tell from the pics but I agree that the inlet area is a little small. It could also be improved by smoothing out the transitions into and out of the hoses.

something like this would probably help
https://www.miataturbo.net/attachmen...ine=1340478496

How are the pressure differentials across the oil cooler? Is it relatively low pressure on the side we can't see?

+1. Look like you are air is exiting into high pressure wheel well.

it exits on top of the undertray to the side of the front mouth ducting which should be relatively low pressure. i am no aerodynamicist though. going to take it to the track like this and see what happens. if it does not work i will just have to move it back to where it was at the track and go back to the drawing board. wonder how well a a fan would work??

A cheap magnehelic pressure gauge off ebay will take all the guesswork out of your ducting.

http://autospeed.com/cms/title_Optim...0/article.html
tells a bit about them. If you search that site for "magnehelic" you'll find quite a few articles.

If you're going to go with a fan, you could try using the 12v bilge blowers Spooky uses for brake cooling in his ducting thread.

Also one thing I note about your original oil cooler location is that it's in front of the cool side of the intercooler, so all the heat being pulled out of the oil was going into your charge as it exited the intercooler. Perhaps moving it over to the hot side (driver's left) and letting the exit half of the intercooler see unobstructed airflow would solve IAT problems without having to use a fan or blower on the oil cooler.

Just ran the numbers for my 13"x7.5" Setrab. I would need a 6" OD tube, or four 3" tubes... yea, that's not gonna happen.

decided the first idea wasn't going to work so here is the mk2 version. it aint pretty but it should work and i am confident will have a large effect on my inlet temps.

https://www.miataturbo.net/attachmen...ine=1341394779
https://www.miataturbo.net/attachmen...ine=1341394779
https://www.miataturbo.net/attachmen...ine=1341394779
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https://www.miataturbo.net/attachmen...ine=1341394779
https://www.miataturbo.net/attachmen...ine=1341394779
https://www.miataturbo.net/attachmen...ine=1341394779

The proof is in the pudding. That's an unusual design for a Miata. I don't think that is what I would have come up with but I'm interested in the test results.

its not conventional but if it works it works.... if not we have plenty of spare bumpers. just be good to have nice clean/cool air to the intercooler.

I also have heat soak issues after about 20mins; leaving 10 mins that I'm down on power. Will an IAT activated water injection system last for 10 mins?