I just read Buschur's post about the head for the Evo and how it flows, and he said that two un-named shops had just tossed the stock rods out of their oil pans. Anyboby know who this was and what the facts were about breaking the rods such as mods, boost, gas, ect? So far there has been a lot of speculation running around as to if the Evo 8 rods are cast or forged, and what kind of pressure they will deal with reliably. Well, if two different shops found out the hard way then I would really like to know how it happened as I cannot afford a short block (at the very least). Normally when a rod goes, so to does the block, especially if some of the rod is left on the crank running around beating the **** out of the block and everything else. I hope that it wasn't one of the guys at the SCC Evo shootout, but I would not be suprised if it was.

 

I tossed number one out the front and back of the block. I dont know who went through the oil pan. No one else blowed up a motor at the EVO Shootout. The coolest part is that the pressed in piston pin was clean out of the rod and piston. Violent stuff. Lots of cool noises, spectacular debris field. The rod failed right in the middle with the bloody stump still spinning nice on the crank journal.

Walbro fuel pump died at 30 psi boost. Put the stock fuel pump (and a used EVO 4 motor) back in and it run fine at up to 25 psi so far. I wont be in a big hurry to play at 30 psi for a while. It had been making over 500 hp for about a month with no trouble. Then two days before the shootout we started having intermittent lean episodes. Narrowed it down to the fuel pump about one sputter-kaboom too late.

Mike W

 

So would you contribute the blown engine more to the lean condition or was it going to happen one way or another? 30 psi is pretty damn high on the stock rods one way or another so I have to wonder how long they would have held anyway. Someone else at a shop I go to has mentioned that Walbro have been known to konck-out and very inopportune times. I would think that we would have heard of many more cases at least in other types of cars if there was much substance behind this however. Do you think that the pump was simply overstressed trying to keep up with that large of a fuel demand?

 

Mike,

Nice *** busting job on the car to get it back out the next day. You must have a heck of alot more motivation than I have left in me!

Nice job.
David Buschur
www.buschurracing.com

 

Mike, my understanding is that the Walbro is at the extreme upper limit of its performance envelope at 500 hp. If someone wanted to use one for 450whp, do you think it is enough pump?

 

I haven't heard anyone mention the OEM Supra fuel pump which has been stuffed in DSM gas tanks for years. Is there a reason? Flow limitation? They are very reliable and less noise than the walpro. (if you could hear it in an EVO ).

Speedlimit....

 

As far as rods holding 500hp. I really think it's in the tuning. If the stars line up (No lean condition or detanation) RRE motor would have held up fine at that power level. Not to say if you are trying to bulid a 500hp that you should not upgrade internals but just that it's possiable to have that much power with stock rods and pistons and have it for a long time with some sence of reliablity.

Being a wrx'er the USDM EJ20 will only make 330whp (dynojet) just before the rod snaps. Just the rods are cast and that all they can take. Now the pistons are fine for that level and I'm sure are fine for even more power. But at those levels when a car starts to knock the stock USDM pistons will shatter (braking ring landings).

sorry to hear that RRE!!, Bosch and HKS make 310ml pumps that can better support that power. Or the Supra guys are using dual walbros in tank.

The Supra guys are another example of what a well engineered stock part can get pushed to. 1000whp with stock bottom ends.

Oh IMHO.

 

It's a bolt on but not as plug and play as the walbro. The Supra Pump would have not helped over the walbro. They are rated about the same.

 

A magazine recently tested several different pumps and if I remember correctly Eric is right, the Supra pump was not much different from the Walbro.

And by the way, I agree with David, RRE showed a lot of fortitude in swapping out the engine in that short of a time frame, they really wanted to compete in order to go to those lengths.

 

The Supra pump (also Cosmo pump and any other 52mm diameter Denso pumps) are too big to fit in the stock fuel pump/filter housing inside the gas tank. It would take a major re-engineering operation to fit one in. I am not impressed with the reliability of the Walbro pumps, but they are enticingly cheap. Running them at high pressures is what makes them die off really quick it seems. Guys running 30ish psi and also guys running high ratio regulators (like on a NT conversion) kill them off pretty quick. They do have their place in the world. Put it this way, we dick around and push the limits of things so you don't have to. I contribute the dead rood to it not being up to all the fuel/no fuel sputter-popping at 30 psi. With everything perfect, you can get away with lots of power on stock components. stronger pistons and rods and head gaskets don't make power, they just buy you safety margin so you can screw up some and live to tell about it.

Here is a flow test of the stock pump vs. the Walbro 255 lph high pressure pump:
http://www.roadraceengineering.com/f...pflowrates.htm

We are rally guys. We are used to working all night to keep a car in an event. We don't wake up fully till the sun goes down and some crew members have actually burst into flame in direct sun light. I had a EVO 4 motor left over from when we bought a motor/tranny to get a tranny for a rally car.

When the motor blew, oil went all over the DP heat wrap and soaked it pretty well. Had to take the car for a little shake down run through the neighborhood to make sure all was good in the morning. So once we started driving the car again with the new motor, it was smoking a lot. I mean... A LOT! We were just driving along doing our best to blend in to the few cars on the road. As much as you can blend with a Fast and Ferocious 500 hp EVO fully riced out with a smoke plume coming out from under the hood. We round a corner and a CHP officer in a parked cruiser is having a junker car towed. We shift up 3 gears and try to tippy-toe by. Just when we think we made it past safe, a motorcycle CHP officer decloaks from nowhere and lights us up. We think we are screwed because the car is so loud, looks crazy, is fully illegal under the hood. If they take the car from us we will miss the contest.

At first he thought the car was on fire when he saw all the smoke. We said "No, it's ok, it just does that" Hahaha. The other CHP pulls up too and jumps out with a huge fire extinguisher and tells us to pop the hood so's he can put caustic yellow powder all over the motor. "Ummm... no thanks, really, it will stop smoking I promise" (really didn't want to pop the hood open). Smoke eventually dissipates and the motor officer tells us he pulled us over for "multiple equipment violations".

The cops both turned out to be really cool. They hear and buy our long story about blowing up the motor for the magazine and staying up all night to fix it and get it running again (I am sure our lovely morning hair and that special "up all night smell after a day at the track" helped sell that). Him and his buddy like the car, know about EVOs and WRXs and hate rice boyze. It was a good day to be over 40. They asked us about our racing and about the shop too. They said they had stopped some of our customers before too, they remembered the shop name (I don't know if that is good or bad :-P )

So the cop from the cruiser pulled out a little digital camera to take a picture of the car. I asked if I could take a picture too. They laughed and said no problem. Let us go clean.



It looks worse than it is there. We are all laughing.

We had some loose hoses when we went on the road course and we were down on power some. Nothing more sleep wouldn't have helped. I had the boost set much more conservative to be a little safer the second day.

Mike W

 

That's good to see officers doing there job and being cool still.

 

you guys are dedicated, and that's why I buy from you

 

Years ago, probably 97-98 or so I read about some Australians who had noticed a problem around 500whp in their IV, V, and VI's where they were actually breaking the crank, and that they had spoken to the guys at JUN during a race and their R&D people said that most of their decision to build a stroker kit was out of the need for a stronger crank and not displacement, which was an added benefit. Not sure if this issue has been addressed by Mitsu in the subsequent generations or will we soon be seeing someone stateside blow the big one.

 

Oh our cranks are a non issue.

 

oh ok, does anyone have any sort of information on the internal specs of the IV-VII motors? Im guessing there has been some sort of development along the way, although everyone only seems to list and mention the supporting hardware that has been upgraded.