(Post Master Supreme)

11/08/08 04:55 PM

BSFC turbo vs. supercharger efficiency

Looking on http://www.rceng.com 's fuel injector calculator, they have this note at the bottom:

* Brake specific should be .45 to .50 for naturally aspirated engines,
.55 TO .60 for supercharged engines,
and .60 to .65 for turbocharged engines.

Maybe I just don't understand but shouldn't the bsfc for a turbo engine be lower than for a supercharged engine? I've always been told that turbos are more efficient. Do you want a richer a/f ratio with a turbo vs. super?

(Post Master Sr)

11/08/08 09:07 PM

Re: BSFC turbo vs. supercharger efficiency

My guess is because they're more efficient at compressing air, you need more fuel to make the mixture right. Sound right-ish to me anyways.

(Post Master Supreme)

11/09/08 09:18 AM

Re: BSFC turbo vs. supercharger efficiency

So like 10-15 years ago some people thought you had to run turbo cars rich so that they wouldn't ping. Some loudmouths got on the internet and proclaimed their "learnings". This was back in the day of things like AFC hacks and RRFPR's on your local grocery getters. Well the truth is on an AFC hacked car running richer also brings timing more back into check. On RRFPR cars, they were going lean up top and nobody really cared enough to spend the $800 that it cost back then for a wideband. Then their were other reasons.

At any rate, you can run turbo and NA cars with similliar AFR's these days. If you paid attention to proper compressor size, intercooler size/design for your application, and designed for a target charge air temp, and the motor is designed to work at this level, you don't need "bandaides" such as running pig rich.

Go to youtube and watch some videos of turbo cars that have been running for a few seasons and thus a lot of tuning time into them. You will see little or maybe a thin vapor/grey trail of fuel behind them. The same thing of cars on the dyno.

I know, I know, your buddys turbo mustang blows black smoke and runs 8.8's at 140mph. I'm not saying that you can't be fast running rich, its just unnecessary with a properly set up car.

On my DSM and my Evo. I run NA type BSFC AFR's. The evo has a slightly better cylinder head design and as such I can run mid 12's and it works well like that. The DSM has a hacked together setup with some free parts and nights with a case of beer and welder to "design" a charge air setup. Thus it doesn't play well on pump gas and I usually run 12.0's on it. On race gas though 12.5-12.6 is where it runs the best.

So your real question is that you are trying to pick out injectors right? Design for their optimistic turbo BSFC values and that will leave you some headroom for when the weather cools off and you need the extra fuel.

(Post Master Supreme)

11/09/08 10:11 AM

Re: BSFC turbo vs. supercharger efficiency

Yes, I have 1000cc's and was thinking I may need to move up to 120lb/hr to run E85. I found a Neon owner with 750cc's who made 335whp at 80% duty cycle. That gets me to just about 450whp with the 1000cc's. If my turbo can make that much I'll be pleasantly surprised! I'll stick with the 1000's.

(Newbie)

05/14/14 03:35 AM

Re: BSFC turbo vs. supercharger efficiency

What I read I really liked it. Thank you for your information!

(Post Master Supreme)

05/14/14 07:49 AM

Re: BSFC turbo vs. supercharger efficiency

...link to rc helicopters in 5... 4... 3... 2...

$\:\)$

(Post Master Supreme)

05/14/14 01:08 PM

Re: BSFC turbo vs. supercharger efficiency

if you're running strictly e85, then 1300 or even 2000 would probably be better for you. if you already have the 1000s, then just turn up the pressure. (assuming you're not using rc injectors)

(Post Master Supreme)

05/14/14 06:59 PM

Re: BSFC turbo vs. supercharger efficiency

Lol, revived thread. But I did get the 1000s. Recently I decided to go with 93 octane gas and use meth/water injection due to Denmah bad influence. I should have more than enough injector for my goals.

(Post Master Supreme)

05/15/14 09:44 AM

Re: BSFC turbo vs. supercharger efficiency

is the head that inefficient? I am at 480whp on straight 93. Honda though.

(Post Master Supreme)

05/15/14 05:45 PM

Re: BSFC turbo vs. supercharger efficiency

Do you have head flow numbers? Mine looks to only be mildly ported but flows 303 cfm max at .6" which I thought was pretty good. (my cams aren't huge though, claimed duration 258 and lift is .394" at lobe I believe, stock lift is only like .256" though. I know of another Neon guy who did 420 on straight 93, not sure what limits these guys are finding. I'm being paranoid and I figure if Denmah does it, it has to be good.

(Post Master Supreme)

05/27/14 02:30 PM

Re: BSFC turbo vs. supercharger efficiency

It's a stock ITR head, which shouldn't be that much more than what a b16 head does. cams are decently big. 1.8L (81.5x89mm)

(Post Master Supreme)

05/31/14 01:47 PM

Re: BSFC turbo vs. supercharger efficiency

Originally Posted By: Prorezalsya

What I read I really liked it. Thank you for your information!

STFU NEWB

(Jr Poster)

11/05/14 09:47 AM

Re: BSFC turbo vs. supercharger efficiency

It's no secret that Honda builds one of the best-flowing heads out there.
It's tough to compare their flow #'s to anyone elses. especially with the overlap they run.

In either case, to back on Dan's 8 year old post, I do remember the DSM guys that were way faster than me and were running in the 10's for AFR for power talking about having to take a leap of faith with tuning AFRs and getting into the high-11's. This was mostly around the time link replaced AFCs, since AFCs would lower the MAF signal so much it would put the ECU into REALLY aggressive tuning maps, and DSMlink would allow to change injector profiles the correct way, and leave timing/airflow alone.

In DSMs the stock intake/head always lead to knock in #2 I believe, and I don't know if anyone ever discovered if it was due to fuel delivery, port shape/airflow etc. It could have everything to do with the extremely short

On the Wagon, and Saabs in General, they do really well and make good power at 12-12.5. It's a lot to do with the intake/head, but I think a lot to do with the longer exhaust manifold runners allowing for less collision of the exhaust pulses, and less heat/recycling of exhaust.

If only they had not put these stupid cast hypereutectic pistons in...we'd be able to take advantake of the otherwise great engine design.

(Newbie)

05/28/15 08:24 PM

Re: BSFC turbo vs. supercharger efficiency

So your real question is that you are trying to pick out injectors right? Design for their optimistic turbo BSFC values and that will leave you some headroom for when the weather cools off and you need the extra fuel.

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