I'm trying to hit somewhere between 350whp and 390 whp with basic bolt ons plus either an MHI 18k or a flex fuel tune.

For reliability, which is better? I thought stock turbo with e85 would be more reliable until I saw the dyno charts. It looks like an upgraded turbo is able to hit higher power numbers with lower peak torque than an engine with e85/stock turbo. My understanding is that peak torque is killer. Am I wrong? Is moderately high torque at high rpm worse than huge torque at low rpm?

It looks like a very conservative 18k tune would land me at my intended power on pump gas, and would keep torque lower than 330 ft.lbs. I'm leaning towards this option over e85 at the moment.

 

I would start with the e85 tune, and when you inevitably want more power then throw the bigger turbo on there. Just make sure you get injectors with enough headroom for the turbo upgrade.

 

Stock turbo on E85 is fine as long as it's tuned properly. The X can take more timing than needs on E85, which pounds the rod bearings out of it.


18k on pump gas would also be fine. You have to buy injectors and a fuel pump either way. The ASNU 330 pump, and FIC 1100cc injectors are a good routs to go. You'll have plenty of fuel to run E85 with the 18k as well.

 

Since E85 isn't the easiest to find, I'd prefer the 18k...

Let me ask this: assuming the same car gets a decent tune by the same person for each scenario, which is more reliable in your opinion:

1) 18k turbo setup on 93 tuned mildly for 380whp/310wtq
2) Stock turbo e85 tuned for 380whp/380wtq

I would think option 1 would be be safer because of the lower torque number, unless the added boost at redline and higher propensity for gasoline to detonate compared to e85 makes enough of a difference to offset that difference.

 

Both are well in within safe limits with a proper tune.

 

The harder you work an engine, the shorter it will last. That's a fact jack. With that said; the Evo engines are quite stout and are known to last at the numbers you're talking. With a bad tune, engines can blow at STOCK power levels. A good tune is #1 priority above all else. I prefer to keep torque on the lower side than most. To keep the stresses on the components a bit lower and also I have the SST transmission and don't want to do a clutch pack upgrade (not to mention it's my daily).
Don't forget:

HP = Torque x RPM ÷ 5252

so its ALL ABOUT THE TORQUE !

I decided to keep my torque low, and then carry that torque as flat and long as possible; resulting in decent HP:



Also when you work a smaller turbo to the limit two things happen:
1.) The compressor starts to produce HOT HOT HOT air because it is out of its efficiency range.
2.) The small turbine becomes a bottleneck and your exhaust gas temperatures can climb.

My pick would be the 18k, but as mentioned either will do what you want. Just make sure the tune is done by a reputable tuner.

 

I would definitely do the turbo with a safe pump gas tune.

 

Since E85 is difficult to get, I would def go with the 18k on pump gas. With the right setup (O2 dump, gsc S1 cams, intercooler, etc) you can make 400whp, maybe a bit more, with pump gas.

 

Thanks for the info. I'm saving for an 18k setup now. It'll be better in the long run since I might try an exhaust cutout. With flex fuel, the tune would need to be safe for pump gas, E85, both with the exhaust open and closed. Seems like a lot of variables to keep safe. Anybody have an tuning issues with an exhaust cutout?

 

With a proper flex tune neither would be an issue. Availability can be an issue, but considering the corrosive and gumming properties E85 can have on the valvetrain it's good to switch back to pump gas to clean things out every once in a while. Besides that, the only real negative to E85 would be its effect on engine oil if you're not running a recirculating pcv system requiring more frequent changes. Like anything there are pros and cons, just need to figure out what will best suit you and go for it.

 

E85 does not gum up the valve train, nor is it corrosive (methanol is corrosive, not ethanol). Some people have experienced the black goo on the injectors, but not everyone.