Compression ratio with E85

[mikejames27]

Alright, Ive decided on Wiseco HD .040 over pistons but now have to decide on compression. Car will be run strictly on E85 until I get an aquamist kit on. Turbo will be FP HTA GT3586r. Can I get away with 10 to 1 compression running straight E85? Im looking to run about 22-25pds DD. Then use the aquamist 50/50 water/meth at the track with much more boost. Im trying to find out as much as I can since im ready to order. Thanks!

 

[gstryyder]

22-25 psi DD? why would you need an aquamist kit? you could do a whole lot more on that E85 even DD the thing..

 

[mikejames27]

So the 10 to 1 compression is ok then? If I dont need the aquamist with E85 thats just one less expense! I was going to use it just as extra insurance at high boost levels.

 

[mikejames27]

So with straight E85 and 10 to 1 compression how much boost can I run as DD?

 

[gstryyder]

why are you wanting to run the 10:1 CR? just wondering?

 

[mikejames27]

Faster spool, better street charachteristics (not doing the stroker), and to take advantage of the E85.

 

[gstryyder]

10:1 would be badazz. more doen low torque... not that much faster spool tho. but, if you wanna keep it easier on yer tuning in making it a DD i would go 9:1.. you could fudge in more boost also..

run the 9:1 with about 28-30 psi to wake up that turbo... with an E85 timing curve also..

 

[juanpac0]

I don't think you'll get faster spool with higher compression (forgot where but I remember reading about how CR has negligible impact on spool vs doing a stroker setup), what you will be doing is increasing driveability, as you said, and making more power at the same boost over a lower compression setup.

 

[mikejames27]

does more timing help spool?

 

[1gDSM4g63]

I know that E85 doesn't knock as much and running higher compression give better throttle response, but you have to consider what you're giving up. Running higher compression is less airflow and you could be giving up turbo boost and horsepower over low end torque. Secondly running higher compression severely cuts the timing down limiting you top end. Secondly, it severely cuts down on timing limiting your top end power.

If you're really considering better throttle response why not go to a stroker block?

 

[gstryyder]

i would say this for advice. get a 9:1. run higher boost say like 28-30 psi. run more timing until you start to knock and then back off. you will very pleased with your results over what you are thinking of doing.

if your so worried about spool build a stroker.
PLUS... those turbo's come with a TS option... and all kinda housings from FP.. which one did you get??

 

[1gDSM4g63]

does more timing help spool?

Timing and Spool

 

[mikejames27]

I havent got the turbo yet. I want to get everything else back together first. Extra expenses always come up! It sounds like timing is the way to go with E85 as opposed to the compression ratio so 9:1 it is! And I just dont want to spend the cash for a stroker crankshaft. Id rather rev to the moon!

 

[mikejames27]

Thanks for that link! Ill do the 9:1! Thanks alot guys! Besides, boost is just a downshift away!

 

[1gDSM4g63]

Yup, with a big turbo that has a large flow rating it'll never stops spool. It's hard to control your shift point with the surging rpm.

 

[gstryyder]

what will help you the most with your spool is to buy the .84 A/R T4 divided housing...and a divided manifold.

and i would personally get the 82r in that housing...

 

[mikejames27]

I was going to do the .82 3" Vband. How does the .84 t4 devided help spool?

 

[gstryyder]

a divided runner will spool significantly faster than a single large runner of the same A/R... while sacrifing a little top end. pulsing runners and not overlapping valves spooling turbo better. i dunno... go search. . sorry i am tired. haha

its all about the proper divided runner/ divided housing combo that makes some magic happen.

 

[mikejames27]

Alright thanks for the help!

 

[gstryyder]

NP man, hopefully you can get your build done soon and get what you are hoping to out of it...

 

[jrohner]

Stick with your initial plans of 10:1. Why give up 4% hp going down to 9:1? If you're ever going to push your setup to the limit, higher compression will help get the most out of it. Some people are going up to 11:1 on E85 still with high boost and big hp. 10:1 is great on a 2.0 though because of the pistons being flat tops rather than having a dome.

 

[Kastigir]

You get more power by increasing boost than compression ratio.

 

[jrohner]

More yet by increasing both

 

[Kastigir]

More yet by increasing both

Absolutely, but it's far easier to tune the lower your CR.

 

[jrohner]

It's also 'easier' to tune a car with 250hp than one with 600, so lets all recommend that he keep his hp numbers really low to make it 'easier'.