wisp of smoke under boost?
 

Hi all,
I have a little problem. I recently put a T72 ball bearing on my 94 Supra. (I already had a T61 single with all the goodies and it ran awesome, just wanted to upgrade, seeing as I had the turbo off to fix some exhaust leaks). It runs fine, although I had to turn the boost down from 18psi to about 14psi or so to keep it from running too lean.

Problem is this:

When it starts to build boost or when I let off from boosting, there is a puff of white smoke coming thru my vented hood. Can't tell where it is coming from (haven't had the time to get it on the dyno), althought it is coming from the passenger side, so I think it is obviously turbo or intake related. It didn't do this with the T61.

Should the hose from the valve cover be going to the intake side of the turbo to act as a type of PCV, or just to a catch can? It doesn't smoke at any other time. Only under boost and after boosting for a quick second. I know its not serious, but everytime I see it, I instinctively let off, sucks to drive that way.

Thanks in advance for your help.

1) Are you running an aftermarket fuel system? If so, what are the specifications?
2) How much boost are you running on pump gas?
3) Have you tested your compresson? If not, I'd suggest you do...and please let us know what the specific per-cylinder results are.
4) Possibly a dumb suggestion, but if you could take a short drive with your hood off, perhaps you could see the source of the smoke under boost and letting off?

The hose from the valve cover should be going to the input of a catch-can, and then the output of the catch-can shoudl be going to the intake side of the turbo.

I am very experienced in turbos. Aside from owning a ton of other turbo vehicles, I also have a twin turbo 69 Camaro that I built from the ground up, and I dragrace a GSX-R1000 that is turbo charged.

I only tell you this so you don't think you're wasting your time or dealing with an idiot or worse someone who THINKS they know what they're talking about, or bought a car that is way above their knowledge and experience.

I appreciate your help as it takes time and thought to put words to page.

Soooo...

I have a stock fuel system except for the 255lph pump.

As I said in my post, right now I am running 14psi with the t72. I was running 18 with the t61. both on pump gas with no issues. (plugs (iridiums) look great)

I have not tested my compression, but I am confident that my engine is sound. It ran perfect with the t61. It has a good tuneup in it and its a low mileage engine (65k). It doesn't blow any smoke on startup or while running, just the quick wisp on boost.

I'm going to try to get on the dyno this weekend to see whats going on, but I'm not confident as my tuner is flatout and dyno time is at a premium. It should do this sitting still as well as moving down the road.

I do NOT have a catch can, although I am finding out that this is a must. The hose goes straight from the valve cover to the intake side of the turbo between the mass air and the inlet of the turbo. I SUSPECT this is my problem. I think the greater volume of air from the bigger turbo is creating this mystery wisp, just can't see from where.
Is it possible that my blowoff valve is no longer big enough to compensate for this extra air and this wisp of smoke is the excess boost coming back through my turbo, which we all know is bad, and because I don't have a catch can, I see a little oil wisp?

It seems I can't be the only one to have this problem, thats what brought me here...
again, I appreciate your 2 cents...

Ok. Thanks for providing a background. :bigthumb:

With all due consideration for your background, I have to point out that you've put together a potentially self-destructive set of components. It has not been proven that a 255lph pump improves overall flow through the restrictions in the oem fuel system. In particular, the openings inside of the 'banjo' fittings on the top of the fuel tank, at the FPD, and at the fuel rail are all extremely small.

First, please note that the Mkiv Supra Turbo, with the oem ecu, will detonate with 18psi on 93 octane pump gas. Depending on how often you boosted this high, you may or may not have gotten lucky by the ecu detecting the knock and retarding the timing in time to prevent damage. Secondly, you may already know that boost control via wastegate is not absolute. Depending on several factors, boost spikes and boost creep are present in almost every setup I've seen (literally hundreds of Mkiv Supras, many of them single turbo'd). Throw a downpipe in a bone-stock Supra and it'll overboost & spike too. When your T72 spikes or creeps past 14psi, you'll both detonate AND run lean. The oem fuel system just isn't anywhere near big enough for this turbo. Imho, you need to get an upgraded fuel system on your Supra asap.

For what it's worth, note that the last (and only) 2jz-gte that I blew didn't smoke at all until the compression eventually went below 120psi (even though it was 'on it's last legs' when my #6 went down to 140). I am 100% certain that a compression test is a wise and prudent step for your situation at this point in time, even if your compression #s are unrelated to your 'wisp of smoke'.

Agreed...a test on the dyno with the hood open should allow you to quickly find the source of the smoke. In theory, you don't even need a tuner onsite...anywhere with a dyno should be able to strap it down for you - then pop the hood, and do a pull...

Honestly I feel this is unlikely, since 'regular' boost isn't smoky. I'd suggest smoke coming from (for example) an oil leak that sprays directly onto a hot exhaust system component, or an exhaust leak, etc. are more likely possibilities.

I did check all the plugs recently (about a week ago) when I replaced them and they were clean, no piston. I suppose that is in part to my decrease in boost. As I said I was only running 14psi or so and I have a ProFec E-01 boost controller, which I was under the impression that these electronic controllers controlled boost creep. (Is that true in your opinion?) I have a HKS EVC IV on my 69 Camaro and it works mint.

I actually have a set of 720cc injectors and a HKS fuel rail, I just wasn't going to put them on until I installed an AEM ECU. When I installed the T72, I re-dynoed the car to make sure there were no changes. As it happened, it was quite a bit leaner with the increased volume, so based on my A/F ratio, I ended up at 14 psi or so and it seems safe. Is it possible that the A/F is safe (around 11.0-11.5?) yet still run lean and/or detonate?

I thought (from reading many of these posts) that a stock Supra fuel system can support UP TO 500hp or so. My car was only around 460ish rwhp with the T61, and as I recall, right around 430-440 now with less boost, even though more turbo. What do you think?

It sounds like I need to do a comp test anyway just to insure there is no damage. I have a little piece of mind after seeing my plugs, but your right, proof is on the pressure gauge.

I know this info is here somewhere but what should I see for cylinder pressure, and the minimum delta from cyl to cyl?

Might take a little time to check it, but I will do it.

I am leaning also towards some kind of stupid oil leak. I think dyno is the best and easiest and safest way to find this out.

Look forward to your reply. Thanks again for your input. gotta go to bed, 4:30 comes quick...
Mike

Unfortunately, no...boost controllers only control the wastegate, which only indirectly affects boost.

I suspect you're running a lot less boost on your Camaro. A larger V8 also has a lot more exhaust volume at low rpms, which tends to drive the turbo with a bit more stability.

Fwiw, I'd advise against that plan. In general, you need to be able to flow enough fuel to match the max airflow of the turbo.

At 14psi on 93 octane gas you won't detonate. Again, the trouble is, with a turbo that big it's nearly impossible to consistently regulate it down to 14psi using wastegate control alone.

Correct. In fact, it'll support 500rwhp or so (depending on whether we're going through a 6spd or an auto).

The key is regulating that boost, and guaranteeing the low boost level with 100% certainty. For example, I'd put big $ on the table that (eg. with a 6spd) if you're cruising in 5th gear at about 65mph, downshift to 3rd and hammer it you can get your T72 to spike up over 20psi, even if your boost controller is set to 15psi. I wouldn't advise it however because at 20psi with that turbo your oem fuel system will run lean. If you also did it on pump gas (i.e. not race fuel), you'd detonate and probably pop the engine within a few seconds.

Agreed 100%.

Yep...it never hurts to know for sure.

Here are the factory instructions:
http://www.mkiv.com/manual/manualtt/...eck/index.html

What part of the car/engine/tranny is leaking?

P.S. Sorry for the delayed response. My computer was down due to a change in residence (i.e. moving).

Hi
Thanks for the response. Guess what I just finished doing? Yep, comp check.
As I suspected, I think I'm good.

Cyl 1= 160
cyl 2=156
cyl 3=157
cyl 4=155
cyl 5=160
cyl 6=155

It looks practically impossible to drive the car and try to see the engine compartment. I am trying like hell to get on the dyno. I'm gonna leave the boost at 14-15 for now and wait until I can find this problem, I'm sure now it's something stupid.

It's not actually leaking, it's letting out a wisp of smoke under boost and when I let off from boost. Absolutely nothing leaking on the floor at all.

Anyway, does anyone know how to convert to MAP? I'm thinking I'm gonna bite the bullet and buy the AEM ECU. I don't wanna deal with the mass air anymore. I've heard it's a simple wire crossover at the mass air connector and change the parameter in the AEM.
Thanks again...
Mike

Good to hear! :)

Cool - good plan.

Yeah but tuning the AEM (or any standalone ecu) can be a whole other can of worms...

Actually you can use the maf wiring for your new intake air temp sensor, but you (usually) have to splice & run wires from the passenger (RHS/LHD) of the engine bay over to the driver's side (RHS/LHD).

I found a guy (experienced tuner!) who has tuned a lot of AEM Boxes AND MR-2's + Supras and it shouldn't be a problem. For now I'm going to start collecting parts for my fuel upgrade and probably order the AEM. As soon as I find my wispy smoke problem, I'll post.
Thanks again for your time
Mike

Please be sure to confirm with him, before you buy your AEM, the exact maximum number of hours of dyno tuning time it will take to get your Mkiv Supra running absolutely perfect in all conditions including cold-starting, hot-starting, good gas mileage for long road trips, low boost on pump gas, high boost on race fuel, etc. etc. Note that (ime) this can take anywhere from eight hours to thirty or more hours. Also note that some tuners charge $100/hr or more PLUS the cost of the dyno itself, which can run an ADDITIONAL $150/hr or more.

Again, good luck with finding the wisp of smoke (I hope it's something easy to correct), and with your planned upgrades.