TT 1UZ power level issues.

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rdm20fan

Member
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212
Location
Near Chicago, IL
Hey Guys,
I've been pushing my 1st gen 1UZ more this past year.
I had a couple problems and I wanted to share.
Maybe a few of you have had the same issues. Here is what I have learned.

13-14 PSI about 450 RWHP issue
I blew out a stock head gasket (Composite) a few years ago right at about 13 psi.

With my rebuild I used the GS400 head gasket (MLS) at 14 psi I would start blowing coolant out of the radiator overflow. This was probably about 450HP to the rear tires. At this point the Toyota head bolts are stretching allowing the compression to get past the gasket, and into the coolant passages. This builds pressure in the cooling system, and pushed the coolant out. On a composite gasket this pushes the gasket out of the way, and you have a head gasket failure. With the MLS gasket it allows the pressure past, but usually re-seats itself when the high cylinder pressure stop.
I kept wasting time chasing over heating issues, when I should have been putting in new head studs.

20 PSI About 600 RWHP issue
Same thing as before, but I was running ARP head studs. It's hard to sometimes think of a bolt acting like a spring, but under the high cylinder pressure the combustion is enough for the bolts/studs to actually stretch until the pressure is gone then they pull back. This is usually the case until it is to much for the bolt/stud to take and it stretches past the point where it will not spring back.

The reason I listed my boost PSI, and what I think the car was making HP level is because I'm pretty sure it doesn't matter how you are making the HP. (Turbo/Supercharger/Nitrous/High Compression, cams) The combustion pressure to make that level of HP is what is lifting the head, not that actual 21 lbs of boost.

23-24 PSI close to 700 RWHP issue
Since the head gasket was re-seating itself after each pass down the drag strip. Chris and I decides to try and up the boost level, and just blow coolant into the over flow.
After each pass we would just drain it, and refill the cooling system in order to try and run a 10 sec pass
(We didn't get there this year)
The motor started breaking up in 4th, 5th gear when the boost levels would get that high.
We were blowing out the spark. The velocity of that amount of air rushing into the cylinder was to much for the coil to continue to drive spark across the sparkplug gap.
We re-gapped the plugs to a smaller gap, and it got better, but didn't go away. At 25 PSI the motor was breaking up bad and wouldn't make any power.

Don't know whats next for my 1UZ. I was thinking of O-ringing the Heads/Block.
Also thought of having the Block/Heads drilled, and tapped for larger studs.
Next would be to also get new MSD coils.

To o-ring, and drill new head studs will probably lead to long periods of down time for the car, and I don't know if that's the route I want to go right now.
The SC is pretty fast as it is. Maybe turning the boost back to 15-17 psi, and enjoying her for a little bit might be a good place to be for a little while.

What do you guys think?

Hope this helps someone going through the same.
Thank, Bob
 
There was a 1uz powered vehicle over here that made 450rwhp N/a (4.5 engine) but wasn't enough. They built a supercharged engine which made 550ish and had head lifting issues. They would retorque the heads several times after each time the engine came apart. Once they started doing this the issue generally was resolved.

Also what size head studs are you running?


Great to see the issues put forward in a clear way too. Hats off to you for doing so. So many times we only see the successes published which make many people think large horsepower is without issues.
 
There are at least 2 1UZ here using ARP studs running much more boost than you do and for greater power with no HG sealing issues. Even my stock setup made 500ish rwhp for ages before the stock HG started to leak.

I would suggest your problems are something other than the head lifting.

What torque setting did you use and did you apply the ARP thread lube? Were they torqued in the correct sequence with multiple passes. Were the head and block (liners) machined at any stage?

Which ECU are you running again and are you sure you aren't seeing any det at all?

There's no reason a MLS/ARP stud combo can't take 25psi comfortably.
 
Hey guys I'm using the stock size studs. 10mm studs I think. It's the set David sells on here. For the ford diesel.
I torqued the studs to what arp recommended. I don't remember off the top of my head what they were.
Torqued them down twice, then came back the next day and re checked them.
Usually I like to run the motor to operating temp, and then check them again, but with the studs being under the cams, I didnt do that this time.
I'm running the stock ECU, so it's still stock timing. I don't think I'm getting any detonation.
I'm pretty sure it's lifting the head at basically those power levels. When I back the boost off it stops, and when I turn it back up, same issue.
The guys running 25psi with arp studs, do you know if they o-ringed the block/head?
I actually did make 510 at the tires on a stock head gasket, but I was trying to be a little conservative with my number for anyone who might be pushing theirs in the hopes of staying on the safe side.

But pretty much have done multiple passes at 19 psi with no issues. 21psi, and I start pushing coolant.
23-24 psi, and the motor starts breaking up from blowing out the spark (I'm pretty sure)
I've done a little research, and these are almost the same psi levels that LS motors are lifting the heads. They also run 10mm studs, and 4 studs per cylinder.

None the less, I think I might try and paint the car this winter, and turn the boost back a little to try and enjoy cruising around in it for a bit.
The carnage of drag racing gets a little expensive on the pocketbook.

Thought?
 
I wouldnt mind betting that the motor is detonating and lifting the head. With a stock ecu ignition timing, at 20 psi it should be sounding like a tin can half full of marbles.
 
Yes im kinda staggered you have seen the power levels you have with the stock ECU and not lunched the engine completely? How many interceptors do you have on there for fuel with boost and to adjust ign timing? or just a rising rate fuel reg?
 
Oh and BTW, the engines mentions weren't o-ringed. My current VVTi build isn't o-ringed either and i intend running 25psi....i'll let you know how that goes :)
 
Generally the LS guys that are lifting heads with boost are using the shittier end of the factory 10 stud heads and that's usually due to the actual deck thickness of the stock heads, the aftermarket companies like AFR run thicker head castings for this reason. From what I've seen of other people and talking with my machinist (worker for mclaren, banks, others and holds current duramax land speed record) he figures the 1uz should be good to easily 30-35psi with proper tune without o-ring or pushing water
 
I wouldnt mind betting that the motor is detonating and lifting the head. With a stock ecu ignition timing, at 20 psi it should be sounding like a tin can half full of marbles.

Yes im kinda staggered you have seen the power levels you have with the stock ECU and not lunched the engine completely? How many interceptors do you have on there for fuel with boost and to adjust ign timing? or just a rising rate fuel reg?

I assumed everybody understood my fuel situation on the motor. I'm running 2 completely separate fuel systems, and 16 total injectors.
I am still running the stock fuel system (Pump/injectors 245cc/tank/rails/ECU/Timing) "or whatever cc the stock injectors are"

I am also running a complete second fuel system. Second tank/Pump/Lines/injectors/rails/additional injector controller) The second system has 900cc injectors running E85. I've been mixing in some Toluene in with the stock tank. This is the reason I am able to run the stock timing and haven't gotten any pre-ignition/detonation.

At 2psi the second system starts adding the E85, my AFR's have been pretty fat. Mostly low 10's



Oh and BTW, the engines mentions weren't o-ringed. My current VVTi build isn't o-ringed either and i intend running 25psi....i'll let you know how that goes :)

Please Do. Any additional info I can get/give is well appericated.
 
which ARP head studs are you using? we were pushing 27-32psi (about 1200hp engine) for over 350-400 1/4 mile passes, 100+ dyno runs, alot of street driving and other driving events using factory size 10mm ARP head studs and 92mm Cometic MLS gaskets, we checked the torque on the head studs only once in that time. they were torqued in at 65ft-lbs, only a couple had let go a little. only time we would see lifting was if the car would run pass after pass over the 1/4 mile without a break, if we let sit 30mins between runs it was fine, however, this didn't start happening until 200-250 passes in, first few hundred passes was not a problem.

what head gaskets are you running? we think alot of the issue with the high boost is with the 92mm head gaskets, because the bore is only 88mm or so, gives the air a bit of room to creep in and lift the heads up. but, that's just our theory we don't know 100%.

possibly there is something else at play as well with the tune that you should look into. we run over 25-degrees of timing with 30psi and E85, and it was fine all that time.
 
Yeah most definitely I agree that it's in the tune, if I read that correctly all your timing is being controlled by the stock ecu? That's a lot of timing to be running with higher boost levels
 
Very interesting information. Thanks for sharing it. I learn a little more, each time I visit this site.

You are welcome. There are a lot of sharp guys on this site. And they don't mind taking the time to share info. Maybe not as much traffic as some, but better then some other lexus sites out there.

Generally the LS guys that are lifting heads with boost are using the shittier end of the factory 10 stud heads and that's usually due to the actual deck thickness of the stock heads, the aftermarket companies like AFR run thicker head castings for this reason. From what I've seen of other people and talking with my machinist (worker for mclaren, banks, others and holds current duramax land speed record) he figures the 1uz should be good to easily 30-35psi with proper tune without o-ring or pushing water

I don't know about 30-35 PSI with just head studs, and MLS gasket, but I'm not the worlds best engine builder/tuner by any means.
I have done a little research, and my motor seemed to respond very similar to what the LS1.2.3 motors are doing. They run a 3/8 (10MM for all basic purposes) head bolts/studs, and 4 bolts per cylinder.

I think part of my issue, or the reason I may be lifting the head slightly premature is changing the head-studs on the motor without taking the head off, and after lifting the head at 14psi with the stock bolts.
I think once I lifted the head (Popped it's cherry) although it would reseal, its probably finding the same weak spot to lift every time the cylinder pressure get high again.

But I'm getting this issue at 21 psi. I can see it handling an additional 15psi, not to mention blowing out the spark on the stock coils at about 23-24.
A couple of MSD coils should help correct that issue.

Anyway you guys have seen what the motor can do on stock timing/ECU. if you want to go the added injector route you should be able to get 600 to the tires. If you want to look into better ways of sealing the head, and better coils it can probably be pushed even further. The ethanol (E85) is the key to the timing.
Love it. it works great, and it's cheap.
 
Yeah most definitely I agree that it's in the tune, if I read that correctly all your timing is being controlled by the stock ecu? That's a lot of timing to be running with higher boost levels

agree, aftermarket ECU is required. $1000-$1500 for ECU or $5-$6k for new motor, i know which i'd go :p
 
For reference on 94octane(~97ron for Paul), 13psi I'm running around 22-23degrees of timing (dyno tested optimal) and if I had to hazard a guess the stock ecu is probably sitting at 35+degrees in roughly the same N/A load cells, well as best as it can deal trying to calculate the air flow
 
on Aussie 98-octane (US 93) we ran 20-degree's timing with 23psi. we were showing about 850hp@motor, ran 9.00@151mph in a 3100lb car.

every engine is different, the 1UZ however is one that responds well to timing on E85.
 


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