I need some opinions from the expert engine builders out there. I built an engine for my '93 MR2 from the ground up. My intentions were to get 350 HP out of it. Everything in it was replaced with aftermarket parts except the block, bare head, & the crank, but it was knife edged, balanced, & polished. Block was bored using a 2" head plate, & head received a full rework. I was running Weisco pistons & a Cometic head gasket. Also had a Walbro pump, 800cc injectors, modified fuel rail with dual inlets, & a aftermarket FPR. Running an AEM stand alone ECU. Turbonectics T3/T4 turbo & Tial wastegate, 3" exhaust.
Here is my problem. I broke the engine in for 800 miles, then took it to the Dyno to have the ECU dialed in for 350 HP at 18psi. At 15psi, it suddenly lost power & #2 & 3 cylinders had almost no compression. Removed the head & these pictures show what I found.
Now the guy on the Dyno says that the head gasket blew, & antifreeze got in the cylinders, causing the pistons to melt. I wonder if maybe it leaned out & melted them because I wouldnt think antifreeze would cause this. Can anyone that is a serious engine builder give me thier opinion? What do you think would cause this? If you look closely at the pix, you will notice aluminum transfer from the piston to the cylinder walls. I figure it got pretty hot for that to happen. The picture of 2 cylinders is #2 & 3 cylinders.
While I have 35 years of expirence as a mechanic, & have built many engines, this is my first turbo engine build, so I dont know if this can happen from antifreeze or not. What do you think?
Coolant didn't cause it.
The burnt piston tops makes me think you went lean, causing detonation.and a blown head gasket.
Without more pics and info, it's hard to tell if the coolant on the piston top is from a blown HG or if it got there when you removed the head, or both.
On a side note, 800cc injectors, walbro fuel pump, fuel rail and aftermarket FPR shoulda been plenty of fuel to avoid going lean. especially at only 15psi.How much fuel pressure were you running?
What about the guy who was doing the Dyno tuning? Did he know what he was doing?
I don't know about what might have caused it, but I agree that all the fuel mods should've kept you far from leaning out, unless it was the tuner's fault or something got clogged/failed.
Where are you in Missouri? Where did you take it to tune?
Well I dont know if thats what happened or not. He is telling me that I left the alignment pins out when I put the head on & it shifted, causing the gasket to blow & coolant caused this. He removed the head, so I dont know if the pins where there or not, but I do know I have built dozens of engines in my life & there is no way I would have forgotten to put the pins in. Plus, I ARP'ed it, so the studs should have held the head in place. I am in Kansas City, but Im not gonna give out the name of my tuner right now because I am hoping he will "make it right" & fix it for me.
I dont know what he had the FPR set at, or the timing either. I wasnt there when this happened.
The dyno guy doesn't know what he is talking about. When a head gasket goes you loose compression and it becomes harder to detonate. Also any coolant that gets into the cylinder evaporates from the heat, undergoing a phase change and cools the cylinder.
The loss in compression was probably because the rings would no longer seal after the pistons started deforming. Also the fact that the pistons melted on the intake side suggests that it was excessive heat in that area that caused it to fail. That is most likely detonation caused either by overheating or too lean a mixture.
It sucks when this stuff happens. Be sure that if you are going to reuse the block and head you have them checked for cracks. If whatever caused this could do that to a forged piston then it could also have damaged other things.
My car is in K.C. right now getting some work. It's at Canaan Auto in Bonner Springs, they came very highly recommended from a couple of big power MR2 guys. It seems like the place to go, you might try them when you get it back together, Josh will take good care of you.
Ok - update - I went to the shop today to look everything over again. The head seems OK, but went to a machine shop for further testing. The cylinders look OK, just need a light hone to remove the deposits. They may have some tiny score marks when honed, but not enough to have an impact on engine performance. Im not about to replace the entire block unless I have to.
I talked with the tuner today & we came up with 2 possible causes. feel free to give your opinion on each.
#1 - Fuel. He thought maybe I was running 87 octain fuel & it caused detonation under high RPMS. I thought it had 91 in it, but I dont know 100%. Could 87 octane cause this under boost?
#2 The way the FPR is mounted caused insufficient fuel pressure. I mounted the FPR (PAXTON FPR) according to the instructions I got online. But he says it is wrong. See my sketch to see how I installed it. The return line comes out the bottom of the FPR, not the fuel rail as I stated earier. He says I should have mounted it AFTER the fuel rail. He says the correct way is to run a line from the fuel pump directly to the fuel rail, then run the outlet line to the FPR & back to the tank. Which way is correct? Could the way I installed it (sketch) cause detination?
Sorry, to yell, but you need at least 91 octane fuel! Otherwise, you run an increased risk of detonating.
Another possible cause you haven't identified is a design flaw in the 3sgte intake manifold. The manifold typically causes lean conditions in cylinders 2 and 3 (on high HP applications).
Like stated, the turbo models do need 91 octane or higher. Do you not know what octane fuel you had in it?
Usually, fuel goes thru filter, then directly to rail with FPR at end of rail in return path to tank.
From your diagram, I can't tell where the return fuel gets into FPR.
I'm also not familiar with that FPR.
Running low octane causes detonation, which causes pitting on the surface of the pistons, and mainly broken ringlands.
Your pics seem to show melted pistons, which is caused by lean conditions, and may not be necessarily due to low octane, but instead not enough fuel and/or too much air.
Ok - update - I went to the shop today to look everything over again. The head seems OK, but went to a machine shop for further testing. The cylinders look OK, just need a light hone to remove the deposits. They may have some tiny score marks when honed, but not enough to have an impact on engine performance. Im not about to replace the entire block unless I have to.
I talked with the tuner today & we came up with 2 possible causes. feel free to give your opinion on each.
#1 - Fuel. He thought maybe I was running 87 octain fuel & it caused detonation under high RPMS. I thought it had 91 in it, but I dont know 100%. Could 87 octane cause this under boost?
#2 The way the FPR is mounted caused insufficient fuel pressure. I mounted the FPR (PAXTON FPR) according to the instructions I got online. But he says it is wrong. See my sketch to see how I installed it. The return line comes out the bottom of the FPR, not the fuel rail as I stated earier. He says I should have mounted it AFTER the fuel rail. He says the correct way is to run a line from the fuel pump directly to the fuel rail, then run the outlet line to the FPR & back to the tank. Which way is correct? Could the way I installed it (sketch) cause detination?
This looks wrong to me. The fuel line should go from the fuel filter to the fuel rail & than to the FPR & back to the tank.
__________________ 89 Supercharged White MR2 5-speed / 09 Corolla S CSM 5-speed
07 Matrix XR Gray Pearl 5-speed (sold 11/23/11)/ 94 Corolla DX Red 5-speed / 95 Previa S/C White Auto/
07 Corolla CE CSM 5-speed/ 10 Prius III Blizzard Pearl
There is a vacuum line to the FPR. It goes in the top of it from the manifold. The line coming out the bottom of the FPR is the return line. I made it that way because thats what the way it was supposed to be according to the info I found on the internet.
As others mentioned, I don't think your FPR is hooked up correctly, but I am not farmiliar with that one so I cannot be sure. I would remove the fuel rail and FPR you have and run it with stock parts. For your power goals a stock rail and fpr will flow enough fuel to the 800cc injectors to have a safe tune; my mr2 makes 363whp at 18psi with a precision 3431 turbo(basically 57trim T3/T4) I am running stock fuel rail and fuel pressure with Sard 800cc injectors and I am only running a 55% duty cycle... I've seen people make ~350whp with 550cc SupraTT injectors and still aren't maxed out on the injector duty cycle! Changing to stock parts elminiates one possible cause of your engine failure.
Another question, did you do a compression test on the motor before this happened?
Once you get your issue solved I highly suggest upgrading the intake manifold; they aren't cheap, but there are big gains when upgrading if you have a modified engine. This is a good one that doesn't cost an arm and a leg http://atsracing.com/Parts.mvc/Index/ATSMANIFOLD
__________________
-91 Mr2Turbo-363WHP/289WTQ
I'm not happy, More power coming...
Now 386hp/300tq and still not happy
-94 Toyota Pickup SR5-
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