high compression e85 turbo bp?
 

Hey fellas,

I am wanting to get some opinions on a e85 1.8 bp turbo build I'm working on. Its a street car with ac, shooting for 400whp. I have e85 readily available and will be running 93 oct when not in home area(ms2 dual map switch). My only concern atm is what compression ratio to run with e85? I have mixed feelings. Ive researched and obviously the evo and honda guys have good results, but then ive seen other builds where lower compression and e85 makes more power at the same boost (subaru guys) if that makes sense. I just ordered 9:5:1 supertechs 84mm and am wondering if its a happy median or what other miata heads think? I already searched on here, not alot of real life results. Please give educated responses.Thanks in advance!

Build info:
1.8l bp
84mm supertech 9:5:1
Pauter rods
Bp4w solid lifter head
Exhintake cam mod
Gt3076r .63ar turbine
Ramhorn ss manifold
75mm throttle body with big plenum intake mani
1000cc injectors high imp
6an fuel lines dual walbro 255

9.5:1 is a compromise ratio, which is a nice way of saying that it does a shitty job on every fuel available. You'll see marginal gains over 8.5:1 pistons on E85, but not nearly what you would see if you did 11:1 and deshrouded the head back to ~10.5. It will also make WAY less power on 93 octane than you would on a proper 8.6:1 setup.

Having said that, if you plan to run E85 a lot (I mean like 50% of the time, and not just a tank a month or whatever), but you still absolutely have to have a pump gas option, then 9.5:1 pistons are probably the best option available.

Experience: Lots and lots of time with a 350whp E85-powered VVT 1.9L.

My previous build was exactly what you're talking about. Used 9.5:1 and it was fine on both fuels.

Experience: lots and lots of time with a semi-built 300whp e85 powered '00 1.8L

Currently putting together a semi-built 350whp e85 powered 1.8, this time going with 10:1

If I wasn't compromising and built this thing all out, I'd definitely do what Sav suggested and go with much higher compression and headwork

You will notice that higher compression turbo builds are associated with bigger camshafts and better heads. Proper cylinder head and camshaft development is one of the more expensive parts of a big horsepower build.

If that kind of time and expense is in your budget, then it is a viable option. If not, stick with the tamer compression.

Keep in mind that high compression big camshaft motors are volatile, and do not take kindly to tuning mistakes. If you lack experience, I would suggest sticking with a tamer motor, and as you build experience work your way up to the big boy stuff.

Well I'm pretty experienced with tuning/building the bp I just wanted to see if anyone had concrete info on 400whp + e85 setups. My last setups made 300+ whp on hydraulic bp05 head and high boost so I expect a lot more power now. So what do you guys think about the cylinder pressures on low comp high boost (30lbs) e85 vs med comp high boost e85(30lbs). I doubt less power and better off boost transient response, but what about head lifting, etc? Thanks

I’m about to build 350-400whp E85 setup. Last year I made 285whp (DynoDynamics) on gt2560 with leaky cylinder head and only 14psi boost. and I’m sure it could have been way over 300whp with 18-20psi. This year with gt2871 plan is run all of it :crx:


I have 9.5:1 supertechs but now I kind a wish I would have gone with the 11:1 cr. There’s maybe only 2-3 occasions in year that I have to fuel normal petrol.

Those are good numbers for a smaller turbo! Well hopefully soon ill be done with the build and get some empirical data of my own. The e85 miatas I've seen are 350whp+ , so I'm excited. So no one can chime in on cylinder pressures?

What about them? To make more power you're increasing cylinder pressures, or you're improving flow with headwork and cams. Do both if you really want to make some nasty power. I don't think anyone here has lifted a head with ARP hardware.

Why on earth would you lower compression when trying to make power? Specially when you are planning on running corn/93 when corn isn't available. To make power = increase cylinder pressure. (Ie: higher compression, more boost) in order to do either of those you need to look into fuel (which you've already decided on corn +++ for boost) so why would you up your fuel quality without taking advantage of it? That's like running a turbo with the charge pipe disconnected.
Be a man, run 10.5:1 or higher. Anyone that tells you that you can't shouldn't even change spark plugs.
If someone says you can't run that high of compression,
a) they don't know how to tune properly
b) they're tuner told them they can't and he doesn't know what he's doing.
c) both a & b

Sorry for the rant, people can unleash some more ponies just from a better parts selection
Good day to you all

This is assuming that you can run all the spark you want. You can have infinite cylinder pressures, but if its not at the right time you're just spinning your engine backwards.

Hence the comment made about not knowing how to tune. I should also add whether or not your ems is capable of handling it. But imo if your doing a stock turbo long block sure mega squirt is fine but if your trying to make power, first thing I'd ditch would be MS. Up your game to an ems4.

Back to the OP, none the less lowering your compression Will Not wield you more power. That's performance oriented engine building, backwards..

Have you used an EMS4? I barely has enough I/Os to run a basic turbo miata, the airflow and fuel logic leaves a lot to be desired, it requires an additional noise filter in most cars to use the better NB cam and crank sensors and it doesnt support AEM Net like you think it would. The tuning software is actually not that bad. But mine's likely going to get ditched for the MS3 pro I should have bought the first time over the winter. The EMS4 seems like the Jesus savior of stand alones, its not all that its cracked up to be, at least its "cheap".

Why do you need to use the stock sensors? It's a standalone, get a crank trigger (or similar). Once again it's not for the novice car enthusiast. Like it's advertised, it's a universal standalone. If you don't want/know how to make it work. Pay someone to do it right the first time.

/\ Looks like we have a new Miata tuning master in the house. Wow! I am so enlightened now!

Sounds like a n00b fluffer trying to come across as a smart guy.

lol

He will soon be "familiarized" with this forum

Fellas, here's the link to the thread that got me thinking about a low compression e85 build, possibly. It is only one case, however its note worthy. I normally build high hp pump gas cars, which is why I wrote this thread, to get educated on others experience with bps and e85. Don't argue and get salty about others opinions. Also, just to be clear (not arrogant), 300whp is not what this thread is about, that's cake on pump gas. I'm talking upwards of 400whp. So far I've seen jonptp make 400+ on e85 and soviet.


http://forums.nasioc.com/forums/show....php?t=2224148

Must be why 8.6:1 pump gas motors consistently make more power and torque than 9:1 pump gas motors. :hustler:

You have a lot to learn about BPs and tuning them.

https://www.miataturbo.net/attachmen...ine=1366163109

https://www.miataturbo.net/attachmen...ine=1366163109

https://www.miataturbo.net/attachmen...ine=1366163109

Unless you have two accounts, I wasn't talking to you.