High comp. +boost vs. Low comp. +more boost - Page 2 - Boost Forum

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Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 5:24 PM
Hey Matt, what's your opinion on me running e85 for now before I build the motor. Right now as soon as I get my portfueler, I will be running 12lbs, super 16g, all stock motor. Any benefit? Or stick with 93

Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 6:33 PM
I'd do it.

http://www.hotrod.com/news/1503-power-in-methanol-racing-alternative-fuel/

I realize methanol is not the same as e85. But If you put it somewhere between gasoline and methanol (where it is in reality), you can see there are positives for making powrr running it. I feel like that article sums up why id run it

You will need more fuel than with gasoline, but you'll make more and safer power with it.

Not to mention it's cleaner. Every time I took my motor apart it looked brand spankin new inside.


I'm going to be converting my mustang to it in a couple weeks (2013 5.0) and its n/a. I still expect a power boost from the change.

If you have it available to where you can regularly fill up with it? Do it.





"A car just isn't a car without a little blood, sweat, and beers." -- Shadowfire
Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 6:34 PM
Please correct me if I am wrong (which is very possible), but I thought the stock J PCM is incapable/has a hard time dealing with E85 fueling requirements?
Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 7:12 PM
I plan on leaving the 32lb injectors in the main rail. Adjusting the fuel tables accordingly and then tuning the portfueler for the boost part. The short and long term fuel trims should adjust somewhat right?
Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 7:15 PM
Akizzem wrote:

I plan on leaving the 32lb injectors in the main rail. Adjusting the fuel tables accordingly and then tuning the portfueler for the boost part. The short and long term fuel trims should adjust somewhat right?

No, in power enrichment mode there are no fuel trims. What's in the ve tables is what you've got.



"In Oldskool we trust"
Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 7:22 PM
I'm not a tuner, but wouldnt it pretty much be the same as tuning for bigger injectors? Since it won't have anything to do with the boost? I'm not claiming to know, but I'm going to have to talk to my tuner and see if it's something he will want to try.
Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 7:35 PM
The issue is that with the stock j pcm you cannot command another AFR ratio in closed loop, you're stuck with 14.7:1 for gas. Stoichiometric for E85 is more like 9.89:1 but it varies depending on the mixture you're actually getting.



"In Oldskool we trust"
Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 7:41 PM
wont the O2 sensor adjust for lambda? It's not wideband sensor, it looks for rich/lean condition. Right?
Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 7:49 PM
You don't want to drive around with 25-30% fuel trims. And open loop operation will be garbage.



"In Oldskool we trust"
Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 8:06 PM
Quote:

I'm not a tuner, but wouldnt it pretty much be the same as tuning for bigger injectors


Yes. sorta.

The J pcm reads in lambda, so any differences in stoich values for gas or e85 are moot. lambda 1.0 is stoich no matter the fuel. (the pcm could run the motor on kerosene if the fuel would work in the motor, if that makes sense)

To get the fuel trims right; force closed loop and adjust the VE tables to get to 1.0 lambda again. then re-enable open loop and your trims should be spot on. Thats how we did my car (of course we did it with the front o2 disconnected, but the result is the same).

This of course follows setting the injector constant, VE offset, etc. I know my injector constant for 80s was not what it should be based on the formula. But this was because we needed more fuel up top, we also used the IPW multiplier to get it more precise. But that is all stuff that can be done regardless of fuel used.



Car ran gorgeously all the time. Only issue was alpha-n and 35psi boost lol.






"A car just isn't a car without a little blood, sweat, and beers." -- Shadowfire
Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 8:11 PM
Matt Linke wrote:

To get the fuel trims right; force closed loop and adjust the VE tables to get to 1.0 lambda again. then re-enable open loop and your trims should be spot on. Thats how we did my car (of course we did it with the front o2 disconnected, but the result is the same).

This.



"In Oldskool we trust"

Re: High comp. +boost vs. Low comp. +more boost
Saturday, February 21, 2015 8:27 PM
So wouldn't it work a little better for me because I'm not tuning for boost on the stock ecu? I'm basically trying to get the motor run stock but on e85
Re: High comp. +boost vs. Low comp. +more boost
Sunday, February 22, 2015 6:07 AM
absolutely

Out of boost the car ran like stock.

Cold start was no problem. Warm start after running though was a little iffy until we messed with the cranking ve.




"A car just isn't a car without a little blood, sweat, and beers." -- Shadowfire
Re: High comp. +boost vs. Low comp. +more boost
Tuesday, March 03, 2015 10:11 AM
To the OP, you are limited by the fuel you are using. Lowering static compression buys you room for more boost on a given fuel. Changing valve lift, duration and overlap can to an extent do the same thing. Eventually you have to ask yourself, what's the purpose of the build? Is it a fun daily driver? If so I'd stay away from lower compression and limited availability fuels lol. Is it a 1/4 mile only track car? Auto-X? Weekend street heartbreaker? Basically ask yourself how much does drivability matter and how much does powerband matter

If you are stuck with 93 octane pump gas, lower compression and more boost (more airflow) will likely net you more power somewhere along the way (FOR TURBO). That's assuming fuel is your limiting factor, not that hardware is going to break along the way. E85 is a different animal. Run it with common sense, and it won't knock, so the high compression and higher boost scenario is favorable.
Re: High comp. +boost vs. Low comp. +more boost
Tuesday, March 03, 2015 10:24 AM
The car is a daily for now. E85 to me is something Ive always wanted to try. Its all over here and it's like race fuel for 1/3 of the price. The car will never do Autox as of now but will see the drag strip now and then. Mostly I want what anyone wants a fun dependable car but power and reliability don't go hand in hand. When it comes time to build the motor I realistically want 400whp. Not sure if I will come close to that but I figure with e85 and a super 20g turbo it might be obtainable. With high compression. If all else fails I'll stick with low compression, maxed out super 16g and 93oct. Which should still be good for over 300whp. I'm just weighing out my options to obtain the goal I have. Maybe lower compression, 8.9:1 with a high boost super 20g would net me 400whp. Maybe it's too unrealistic. These are the things I'm trying to find out.
Re: High comp. +boost vs. Low comp. +more boost
Wednesday, March 04, 2015 4:33 AM
Based on what LNF/LSJ guys do with the s20g (on lower compression ratio and displacement than a stock L61) , you should be able to max it out and get ~400whp on pump gas, and very certainly on E85. There is a guy in my area building a forged L61 at 8.9:1 compression with comp turbo cams with the same goal on pump gas. I think he will get there. It might be a bit of a slouch out of boost, but it's not his daily driver.

One other consideration - low comp and "bigger" cams = big hit in fuel economy. You have to press the pedal down more and rev higher to get the same output and that affects economy directly.
Re: High comp. +boost vs. Low comp. +more boost
Wednesday, March 04, 2015 7:20 AM
I think the ln2 I had was low 9's:1 compression. I shaved the head a little so it would be a bit more than stock. Dunno how much though.

I would guess I was around 400 at the tires on a gt35. So with an l61 or any iteration of the dohc motors you can do 400 on 8.9 with enough boost.

If I knew what I know now when I bought the motor parts I would have went with higher compression.

My mustang is 11:1 and I plan to turbo the stock motor with 0 worries on e85 and get around 700 out of it. (I plan to build the motor in a couple years and make more). Granted I don't think it'll take much boost to get there.





"A car just isn't a car without a little blood, sweat, and beers." -- Shadowfire
Re: High comp. +boost vs. Low comp. +more boost
Wednesday, March 04, 2015 1:39 PM
For your goals stock compression or slightly higher with a 20G and you will hit it as long as you have a good tuner.



FU Tuning



Re: High comp. +boost vs. Low comp. +more boost
Wednesday, March 04, 2015 1:43 PM
Addicted to meth wrote:

For your goals stock compression or slightly higher with a 20G and you will hit it as long as you have a good tuner.

X2



"In Oldskool we trust"
Re: High comp. +boost vs. Low comp. +more boost
Tuesday, March 10, 2015 6:54 PM
Haven't been on in a while or I would of chimed in! My car has flat top Pistons, with the head shaved, I'm figuring about 10.5 to 1. With a turbo like a gt30 (maybe one of these days I'll look and see what it is exactly). I'm planning on running 25-28psi, on e85. I'm going for a street/strip car. I'm not worried about it at all! I over built the engine, so it could take some abuse! Everything internal should hold at least 500hp, I don't think it will ever brake 400hp😉! Like other people said decide what your building!


Built and boosted 2.2 ohv
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