Turned down boost...how much hp per PSI do i lose?

[JoeyJigglesGSX]

I'll make this simple and then if you need more info. i can explain...

I had to turn my boost from 25psi to 18...about how much hp do i lose? i have an EVO III 16g

 

[donmagicjuan]

wow...newturbotuner, where did you learn how to do this tuning stuff? did someone teach you?

First off, good post NewTurboTuner. If you check out the Tech Articles in these forums, I believe there are some very helpful threads that cover the basics of tuning, although it has been summed up rather well here. Keep in mind, however, that an S-AFC will not permit you to alter your ignition timing curves. The only parameter you will be tweaking when tuning your car is the air/fuel ratio. Unless you're running larger than ~660cc injectors, tuning with an S-AFC can still net you some appreciable gains without incident.

 

[NewTurboTuner]

Thanks guys. I'm glad I can help!

....If ya don't mind I'd like to tell my story on how I got started with tuning.

It all started back in 2001 with my N/A TransAM WS6. At the time I had Full Bolt-on's. Full intake, gutted 3.5 MAF, and full race exhaust with long tube headers. After I installed the full race exhaust, I was disappointed because It cost me near 1600, and I only gained 13rwhp, and 8rwtq. (back then I dyno'd after every mod, to see the gains) While on the dyno I noticed my stock tune was running like 10.1 A/F ratio. ~I went home that evening disappointed with my gain. I didn't know why I gained so little HP, but I did know I had to fix my Air/Fuel Ratio's. So that night I ordered up a MAF-Translator that would let me adjust it. After I got the MAF-T I didn't have a way to see what my A/F was, so I had to go back to the dyno and get some o2 readings. I got to the Dyno and did a baseline run with no changes made. I got the same thing as last time, 324rwhp. It was still super rich, so I got out of my car, popped open the MAF-T lid, and I turned the dial to -5% fuel. My next dyno run I gained 19rwhp!! (Keep in mind that is on a Naturally Aspirated car, with ONLY a Air/Fuel adjustment!!) The guys at CarbConnection were like... "What Did You Do To It!?!?!" haha! I was amazed!!! I didn't think that was going to happen... I just wanted to get my A/F ratio's in check. I wasnt expecting the big gain in HP. ~That day I left there with 343rwhp, and was starting to notice the importance of a good tune! ...Heck I changed 1 thing, and gained 19rwhp!! So with that in mind, I wanted to tune the car even better! ...A month or so later I ordered LS1 Edit... which is just like DSM Link, but for LS1 motors. After I got LSI Edit I was real excited to go to the drag strip, and see what I could do with it... I went to Pacific Raceways (I think it was Seattle International Raceways back then) My A/F ratio's were still ok at 11.7, and my 1st pass was 13.1 @108mph (which I wasn't happy with) ...So I started messing with my timing. And what do ya know my passes became faster and faster until I my final pass of the day was 12.7 @112mph! ...I gained 4 tenths, and 4mph with ONLY TIMING CHANGES!!! ....I was freakin happier than a mofo!!! ((Before I was amazed at the HP I gained with just A/F ratio changes. And now I couldn't believe that just a timing change would make that much difference in performance!)) .......From that day on, I was fully hooked on tuning!! I started with full bolt-ons and got 324rwhp, Then tuned the car ending with 357rwhp! ...In all that's a 33rwhp gain ...maybe 40hp @ the crank! That's damn good for a naturally aspirated car to get 40hp out of a tune! ....And not just any tune ...It was MY tune! Yup! From that day on I was a firm believer in good tuning! After that I tuned everything myself. I put nitrous on the car, and tuned that perfectly. Then I started tuning friends cars ...and it was just a fun thing to do... To be able to tune a car and make it run better/faster


I love still love that story today.
It was one of the biggest lessons I learned when it comes to modding cars. Its not always about all the parts you throw on the car... its how you make them work together that counts. It's a little bit different with Turbo cars, but not too bad (hence the name NewTurboTuner) You start off not knowing anything... then you learn a little, then you learn a little more, and over time (through trial and error) you will have a decent understanding on what works and what doesn't. It can't be learned over night, but once you start to see good results, you will be proud of yourself for what you have accomplished.


Anyway... hopefully that wasn't too boring haha
Maybe it will inspire some of you to go out and tune so that you can see the full potential of what you've already got

Thanks guys!
~SteveB

 

[nightspeed87]

yea you have some good posts... Im sure you wont be a new member for too long...!
When I start tuning my car I know at least one person who I can look for .

 

[JoeyJigglesGSX]

UPDATE:

well i talked to my main local shop and they said that the tune should be fine because my turbo runs out at about 21 psi anyway (i know someone mentioned that earlier) so the tune shouldn't be THAT off if anything...

Also i got on it open throttle in like 4th or 5th gear (i know if any it should be 3rd, but i was on the highway when i though about it) and my wideband was reading (11.4-11.6) what do you guys think about that number?

Last thing, for some reason sometimes when i am sitting at idle, my SAFC will read KNOCK anywhere between (1-4 and even sometimes 8) i have heard the knock meter isn't that accurate, but still...just wondering what you guys thought

 

[spyderturbo007]

Remember that airflow = power and pressure = heat. You really can't relate changes in pressure (psi) to changes in HP. It is easier to relate changes in airflow to HP. A close approximation is that 1lbs/min of airflow ~ 10HP.

11.4 - 11.6 AFR on a turbo motor is really pushing it lean. If you are running 93 octane, you should keep your self in the 11:1 range.

As for the knock sensor on the SAFC, it will not work with our cars. 99% of the people don't even hook it up.

 

[JoeyJigglesGSX]

11.4 - 11.6 AFR on a turbo motor is really pushing it lean. If you are running 93 octane, you should keep your self in the 11:1 range.

Well now im scared...is it really that bad? The guy at the shop said that tune is fine as long as it is under 12, if it ever goes over for some reason then i should get off the throttle and re-tune

 

[slipstream808]

Can you monitor knock?? That's the thing you want to avoid. If you can't monitor knock than yes, stay around 11.0. But if you can monitor knock, then feel free to lean it out to 11.5ish. Your AFR doesn't destroy the engine, detonation does. But detonation is caused by AFR and timing. So tune accordingly!

 

[SRTthis]

Remember that airflow = power and pressure = heat. You really can't relate changes in pressure (psi) to changes in HP. It is easier to relate changes in airflow to HP. A close approximation is that 1lbs/min of airflow ~ 10HP.

11.4 - 11.6 AFR on a turbo motor is really pushing it lean. If you are running 93 octane, you should keep your self in the 11:1 range.

As for the knock sensor on the SAFC, it will not work with our cars. 99% of the people don't even hook it up.

11.4-11.6 is fine... wouldnt go any leaner though

 

[donmagicjuan]

11.4-11.6 is fine... wouldnt go any leaner though

Let's not turn this into an argument about what the perfect AFR is. Any two cars with similar mods can respond to changes in AFRs and timing a little differently. A good rule of thumb is to tune for 11.0-11.2:1, but if you're able to lean it out from there without seeing knock, then that's ok. slipstream808 hit it right on.

 

[JoeyJigglesGSX]

ok, well last night i got on it and it was a cool night of about 60 degrees and it hit about 11.8, but i still hear that his fine for my car...as long as im not hitting 12s at all and obviously 13

 

[SRTthis]

ok, well last night i got on it and it was a cool night of about 60 degrees and it hit about 11.8, but i still hear that his fine for my car...as long as im not hitting 12s at all and obviously 13

11.8ish isnt to bad but id try to keep it under 11.6

also what wideband are you running and how old is the sensor?

 

[JoeyJigglesGSX]

brand new as of last week...AEM

it hit 11.8 at like around the 6,000+rpm point

 

[SRTthis]

ok cool. just checking. some cheaper wideband kits the sensors go bad quite quickly

 

[donmagicjuan]

ok, well last night i got on it and it was a cool night of about 60 degrees and it hit about 11.8, but i still hear that his fine for my car...as long as im not hitting 12s at all and obviously 13

If you're running pump gas and you do not have the ability to monitor knock, I would advise against doing what you're doing. Many DSMs will show signs of detonation at the AFRs you are seeing. Why are you placing the fate of your engine in the hands of some hearsay? Whoever gave you this advice does not have experience with DSMs. If you cannot tell whether you are knocking, you cannot guarantee that you are not damaging your engine. There's an old saying that goes something like "your car will never feel as fast as the moment before you melt the pistons." Do not trust your car to give you an advanced notice prior to a catastrophic failure. You need to either get a logger to verify no knock or richen up your AFR to a safer level. Otherwise, I guess we'll be hearing from you again shortly.

 

[gamingguru]

So, you have an AEM now? Those things are great for tuning, but you can burn a whole in your motor pretty quick if you don't know what your doing. Just don't get to crazy with things until you fell like your confortable with it.

 

[spyderturbo007]

I highly suggest that you richen up your maps. 11.6:1 is too lean when you are running pump gas.

 

[JoeyJigglesGSX]

ok, thanks for all of the advice...just so you guys know, i wasn't sure if you were aware...i dont tune my car, i dont ever touch that thing because i have no idea what im doing...i took it to Extrememotorports.com...they tuned it and i told them to put it at a safe level because it is my daily...im going to call them up and get some more answers and then post what they told me

 

[daren_p]

Yes as a general rule 11.6-11.8 is gettin towards the lean side for our cars, what octane do you run as this will play a role in determining how lean you can run. Do you have a logger or did they tune your car with a logger? If not you have no idea if the car is knocking or not. If you don't have a logger this is something you defently want to invest in, your motors life could very well depend on it. Generally I too like to stay around 11 to 1 on pump 94, running ~20 psi

 

[NewTurboTuner]

Hey Joe
I'm starting to think those guys who tuned your car are full of CRAP!
Major Crap!

OK correct me if I'm wrong.
1st ... you car got tuned at 25psi
2nd ...then you turned it down to 18psi
3rd ...the people who tuned it, said 18-25 isn't a big difference ...so the tune they gave you at 25psi, should work with your 18psi.
4th. Now at 18psi, you see 11.8 A/F ratio on a cold night

If that is all correct then those guys who tuned your car do not know what they are doing. Hell scratch that! They DONT know what they are doing.

.....if you see 11.8 A/F ratio at 18psi, with a 25psi tune.
.....Then with 25psi, that freaking tune must have been phucked up beyond belief!!!

Joe
if you don't have a way to monitor knock.... Right now I would go with a EXTRA safe tune until you DO have a way to monitor knock.

Most people on these Forums want as much power as they can get, out of whatever they have. If you want good performance from your setup, you need to know EXACTLY what is going on inside your engine. If you don't know what's going on inside your engine.... then you shouldn't try to get so much performance out of it.

You should have gotten a logger a long time ago. I suggest that be your next upgrade.... and really its not even a upgrade at this point. It is a requirement.

If you are seeing 11.8 A/F ratio ..... well that's not what I would consider a safe tune.
And 11.8 is defiantly NOT OK without being able to monitor things like knock.

For now (If I was in your position) I'd turn the boost down anther 1-2psi .....that will make the A/F ratio a little safer. I know that's probably not what you want to hear, but its better to be safe than sorry. THEN buy a logger of some kind. DO NOT go spend more money with those people who tuned your car. Save that money for a logger. When you get the logger, we (or I) can help with your next step

 

[donmagicjuan]

DO NOT go spend more money with those monkeys who tuned your car.

Alright, I'll say it. I wouldn't exactly go calling Extreme Motorsports a bunch of monkeys. There are probably some other unaccounted contributing factors.

http://www.extrememotorsports.com/talon.htm

 

[NewTurboTuner]

Yeah I've look at there website before. Just because they build a fast car doesn't mean anything about the way they treat other peoples cars... or how they respect their costomers.

.........They tell him a 25psi tune is going to be good for 18psi? That blows my mind. That is not what a professional says. That is not valuing the customer. Saying a 25psi tune is good for 18psi ...well that's just BS. Anyone that knows anything about tuning knows a 25psi tune does not work well with 18psi.

PLUS ....He is hitting anywhere from 11.4-11.8 A/F ratio with his 25psi tune ...and he's only running 18psi.
What kind of crazy A/F ratio would he get if he turned it back to 25psi? Its no wonder he blew a gasket, and he's lucky thats all that happend. ((Which Joe, you need to fix that ASAP if you haven't already))

.....man something is messed up. that's for sure.

If they really did say that their 25psi tune was good at 18psi ...At VERY LEAST they are giving you messed up advice ....that would be enough for me to stay away from them.

If they don't fix your tune for free... or at least give you a discount to re-tune your car.... I wouldn't go back to them, unless I didn't have a choice.

Maybe the monkey comment was harsh, (I'll change it) but so is the way they've treated Joe. I get heated when a shop takes advantage of someone who is less knowledgeable about cars. I've been there before with big name shops. Its not just the little shops that pull that carp. Its not cool at all.

 

[JoeyJigglesGSX]

Thank you everyone for your concerns...i am stuck in the middle because i have no idea what to do...i called the guy who tuned my car last night and he said he always tunes DSMs to be between 11.5 - 12.1...now after hearing what all of you guys say when i heard him say 12.1 i was shocked. He swore up and down that i was completly ok. After talking to my local shop who are more my friends than just a shop, they took it for a drive because they had to fix the gasket on my downpipe, thats what blew. They said they liked the ratio and it was fine also. And they also explained to me that the reason not to worry that it was tuned at 25psi is because my turbo's 100% efficiency dies out at about 21 psi anyway, so at worst my car was tuned maybe 3 psi's higher, which is not nearly as bad as if it was a true 25psi tune.

Now if i had a ton of money of course i would go and just get it re-tuned, but i dont. I am going to take your advice and get a logger to see what i can do. But i am being tossed around right now by everyone and dont know which way to go. I can tell all of you guys know what you are talkign about and i have absolutly no way to question anyone because i have no knowledge and i accept that.

As for right now i will have to save up for a logger. Its hard not to believe extreme because they were telling me they tune DSMs all day long everyday and have never had any problems. He said he would never tune my car at an unsafe level mostly because i specifically said not to.

Im just going to have to get a logger and shove it in their face when i show them how messed up it may be. Or appologize for them being right. I might have my local shop throw it on the dyno and have their logger check it out for me. Please keep the advice coming and thanks for all of your help.

 

[Ultimatedsm]

You shouldn't really run the EVOIII Past 22 psi. Get it tuned at 22 psi.

 

[daren_p]

You shouldn't really run the EVOIII Past 22 psi. Get it tuned at 22 psi.

According to who Are you talking just because of the knock limits of pump gas or because of the turbo itself? If your talking about the turbo itself, I guess you should tell shapegsx this, who run's ~29psi & runs 11's or the other guys that make some nice Hp numbers running 25 psi daily with WI, etc.

As for just turning down the boost abit to get a richer air/fuel ratio this isn't always the case. The ecu adds/removes fuel based on the amount of airflow the MAS see's.

 

[gamingguru]

Joe, If you have an AEM then it is able to log internally all of the sensor inputs for you. You won't have to go out and get a seperate logger. It might be that there are still the logs from the shops dyno pulls on your AEM? I would check that out first.