1JZ-GTE - CT-12 Wastegates

[Chambers]

Hi all,

I'm working on a 1JZ-GTE Supra and having trouble controlling boost.

Short history:

Client had a local do the swap, from day one he had issues with pulling over 12 psi and hitting boost cut. So he put a MBC on to try to control it, but it didnt change anything. Recently he bought a MAP ECU2 that has EBC capability, witch I have installed and we have got running. The issue of boost still remains.

Ok, this is how it goes, we start off with the EBC. I set the MAP ECU2 to open the EBC at 12.5 psi. On our first road test we pulled 12.4 psi then in the 5k rpm range it spiked to 13-14 and hit fuel/boost cut. On the second test I set the EBC at 9.5 (lowest setting) and the engine still made 12.4 psi then in the 5k rpm range it spiked and hit fuel/boost cut. This, and previous info from the client leads me to belive that the boost issue may be mechanical in nature. Also, I did a visual on the front turbo, the actuator does not look like it has been shimmed out.

So, my question to all of you is; Have you ever had the OEM wastegates on the 1JZ-GTE not open?

Thanks

 

[mkiiichip]

You cant lower boost below wastegate pressure. Boost controllers can only raise boost.

And yes 1jz do hit fuel cut at wastegate pressure (with some free flowing mods)

You need to raise fuel cut, with larger injectors and a piggyback.

 

[Chambers]

Yea, I completely understand the concept of boost controllers.

I know any engine will hit fuel cut when enough boost is added, the only thing this engine has is a aftermarket down pipe bolted to the stock y pipe.

Raising fuel cut and adding larger injectors with a piggyback will not solve my issue of "over boosting." The engine isn't built at all so adding more fuel and boost is not the goal, its a stock engine with stock power goals. And just for info, the MAP ECU2 is a piggyback.

The issue may be the OEM wastegate is not opening or not staying open, so I wanted to hear what others have experienced with the OEM wategate actuators, and any issues they may have had. Although I have never heard of any...

Thanks for the reply.

 

[f00g00]

My experience with the stock pea shooters is they put out with stock ecu and no mbc around 8 to 10 psi after my swap and fixing my crushed 1JZ intercooler (crushed on pallet on its voyage to Kuwait from L.A.) with a stock 7M I had. I was thrilled after having boost but of course wanted more so I got a bigger intercooler kit (driftmotion) which allowed closer to 10 -12.
Then I got an MBC and was able to hit 14 + before fuel cut. I finally had to get a FCD to go as high as I wanted. I set for around 16 as any higher and it got spikey and surged a little. I had a set of twins upgraded to steel wheels and had them installed and when the stockers were removed, the back one had some fairly large chips missing from the blades so I think the surging was from that. The wastegates can be contolled to open later by an MBC but you still need an FCD to get past cut.
I'd suggest checking the wheels for condition and would guess thats why your getting spiking issues. Im also running a wideband to make sure Im not running lean. Im able with the stock injectors to get an afr between 11 - 11.7 at 20 psi but don't like running that high as the twins even though upgraded start wheezing and stop pulling too early.

 

[te72]

I've never had them get stuck closed, only had one lose the clip that holds the actuator on. One turbo REALLY overworking itself to get to max PSI while the other flushed away all it's potential down the tubes...

As for this cut, is it fuel cut, or is it just breaking up? As always, I'd suggest checking the gap on the spark plugs, make sure you're around the .028-.030 range on all 6. If that's not the problem, I can't say I've had it yet.

 

[destrux]

With just basic intake and exhaust and a FMIC my car was showing 12 psi running with the wastegates hooked up direct. In cold weather it was closer to 14.

If you have a bleed off hole after the WG solenoid (all MBC's do, some EBC's do) then the slight leakage out of that hole causes boost to go up about 1psi over wastegate base pressure (which, if it's too close to boost cut already.... will put you over the edge).

 

[Chambers]

... I'd suggest checking the wheels for condition and would guess thats why your getting spiking issues. Im also running a wideband to make sure Im not running lean. Im able with the stock injectors to get an afr between 11 - 11.7 at 20 psi but don't like running that high as the twins even though upgraded start wheezing and stop pulling too early.

Ok I will do a visual of the compressor wheels to make sure nothing is out of the norm. Thanks.

I've never had them get stuck closed, only had one lose the clip that holds the actuator on. One turbo REALLY overworking itself to get to max PSI while the other flushed away all it's potential down the tubes...

As for this cut, is it fuel cut, or is it just breaking up? As always, I'd suggest checking the gap on the spark plugs, make sure you're around the .028-.030 range on all 6. If that's not the problem, I can't say I've had it yet.

Ohh it’s definably fuel cut, it just "stops" doesn’t break up doesn’t keep pulling just "stops". I will check plugs, and there probably due for replacement soon but one thing at a time right now. Thanks.

With just basic intake and exhaust and a FMIC my car was showing 12 psi running with the wastegates hooked up direct. In cold weather it was closer to 14.

If you have a bleed off hole after the WG solenoid (all MBC's do, some EBC's do) then the slight leakage out of that hole causes boost to go up about 1psi over wastegate base pressure (which, if it's too close to boost cut already.... will put you over the edge).

Ok, we are going to do some testing with the actuators plumbed direct vs through the EBC and see what PSI they hold. As said before, the client said he has always had this issue, so there’s a good chance the local who did the swap damaged something or removed something...

Thanks again for all your replies, any help is much appreciated!

 

[te72]

You'll have to post up when you get it figured out. Nothing like coming across a promising thread when searching for your woes, only to find a dead thread with no solution or explanation...

 

[Chambers]

Ok, so I got a chance to do a test on the car today before the rain started. We plumbed the wastegates up "like" factory, front compressor controls the front actuator and the rear controls the rear. During the test drive the car pulled better than it has ever and didn't hit fuel cut, driver took the engine up to 6500 rpms and let off. The issue of "over boosting" still remained, we pulled ~13psi. I have uploaded a video to help explain, again, this is the actuators plumbed up like stock, front for front, and rear for rear, no boost controller of any kind is on the vehicle.

[video=youtube;CN8iUBlhunU]http://www.youtube.com/watch?v=CN8iUBlhunU[/video]

 

[johnd]

Restrict your exhaust if this is causing to much problems for you. Simple mods like ic and exhaust usually result in 14-15psi on the 1jz. most people like this, as long as you can stay away from fc.
My twins made 12psi until i cleaned out my cat, now it creeps up to almost 15psi when its cool outside.

 

[Chambers]

Restrict your exhaust if this is causing to much problems for you. Simple mods like ic and exhaust usually result in 14-15psi on the 1jz. most people like this, as long as you can stay away from fc.
My twins made 12psi until i cleaned out my cat, now it creeps up to almost 15psi when its cool outside.

Interesting, the car does have a large intercooler, 3" cat back, and a down pipe, still on the factory y-pipe though. When we did the last test the average outside air temps were down from the last time we drove it, so that may have helped keep fuel cut away. So at what pressure are the factory gates to open?

Thanks.

 

[te72]

When we did the last test the average outside air temps were down from the last time we drove it, so that may have helped keep fuel cut away. So at what pressure are the factory gates to open?

Thanks.

If anything, colder ambient temps will increase the chances of fuel cut. Air is a bit more dense at lower temps, therefore the car can stuff more air into the motor without help, so on and so forth... I regularly hit 15-ish psi during the winter with no help other than negative ambient temperatures. As for what pressure the gates open at, I would think 12psi, at least on my set. That is where mine would hold nicely.

 

[Dylan JZ]

Restrict your exhaust if this is causing to much problems for you. Simple mods like ic and exhaust usually result in 14-15psi on the 1jz. most people like this, as long as you can stay away from fc.
My twins made 12psi until i cleaned out my cat, now it creeps up to almost 15psi when its cool outside.

best comment here.. my twins have always been able to hit 16-18psi when it's cold (boost controller has been zero'd out since day one because of this), and probably around 14-15 when it's warmer. these turbos are known for boost creep when a free flowing exhaust is added, and I imagine the FMIC+piping helps too.

restricting the exhaust is probably the best way. IIRC, they do this on the Aristo motors to keep boost in check due to the same issues.

 

[Albert]

You guys can always upgrade the wastegate port on the turbos.

 

[foreverpsycotic]

My stock twins used to push 16psi in 90* weather with intake and 3" exhaust (from the stock y pipe back). IC was stock, boost was measured at the manifold.

 

[Chambers]

Thanks for the replies.

Recently the owner of the car decided he wanted to put a single aftermarket turbo on, he is tired of inconsistant boost pressure and hitting boost cut.

 

[Albert]

<_<. Quiter

 

[foreverpsycotic]

Thanks for the replies.

Recently the owner of the car decided he wanted to put a single aftermarket turbo on, he is tired of inconsistant boost pressure and hitting boost cut.

Good call, easier in the long run. What turbo/manifold setup is he going to go with?

 

[Chambers]

<_<. Quiter

Haha, yea, well If it were me Id be messing with the twins for a little while longer.

Good call, easier in the long run. What turbo/manifold setup is he going to go with?

He is going with GT4088R Dual BB Twin Scroll Turbo, not sure what manifold though.

 

[nctexan]

I think I am hitting fuel/boost cut. I'll start a nice smooth pull then theres a pop and acceleration just stops, check engine light comes on, I just take my foot off the gas and then it goes away and the car is back to normal. It's only happened about 3 times but each time has been when its in the lower 40's. Does this sound like it? I know I need to get at least a boost gauge on the car ASAP, I'm still running the 7M-GTE's. I've been thinking of putting my highflow cat back on (running just the testpipe) just bc of fumes but until I get an aftermarket controller and computer on the car it sounds like it may be a nice saftey net.