Turning Down Boost to get more power?

[TURBOSPYDER]

What do you guys think. Could it be possible to turn down the boost to get more timming and actually be faster than running high boost? Im currently at 1.45 bar, 91 Octane gas, with 20G, 720cc injectors and supporting mods w/ stock bottom end. ANyone have a theory on this? Thanks for all the help.

 

[larryd]

NO .. just tune for your boost.. thats all

 

[TURBOSPYDER]

I guess your right. Last time i tuned for timming, I had a really bad time
I lost power BIG TIME!

 

[Mistaspakles]

1.45bar on 91 octane is very very dangerous. If I'm correct, 1.45bar is about 21.31lbs of boost. You may be experiencing knock and detonation. If you live in Colorado or high altitudes that's one thing, but on sea level, 21.31lbs of boost on 91 octane is way too much boost. I use 92 octane and 17lbs (1.15 bar) is the most I will go on 92. You better check your pistons to see if they are fried.

 

[BrnOutKing]

I run 20bls of boost on 92 oct - tuned on the dyno.

But I have noticed sometimes if I do drop the boost down to 17-18psi.

sometimes my car actually feels faster.

I took down a C-5 one night with only 17psi.

but the night was cold so that might have played a part in the extra HP.


-brian

 

[1QWK4]

I agree with Brian. I was running 18 PSI on 92 octane until I got my pocketlogger. It revealed I was getting a ton of knock which was pulling my timing badly. I turned the boost down to 16 PSI and the car seems to pull harder now that the knock was lowered tremendously and now getting nice timing. Just my .02

 

[L2RTSiAWD]

I also will agree I cannot tune my car for 20psi on 91 oct in 100 degree heat. I turned down the boost to 1.3 bar and I could tune and get great timing curve.

Later,

 

[gst_spyder]

91 octane , man Cali gas sucks, here in MD Sunoco has 94. With the mods you have i'd say it's time to put the Spyder on the dyno and tune it right since it doesn't look like it's going well on the streets since the 720's are making it harder to tune.

Mario

 

[TURBOSPYDER]

ill try lowering the boost and tell you guys what I get. Thanks for the info

 

[TURBOSPYDER]

Originally posted by Mistaspakles
1.45bar on 91 octane is very very dangerous. If I'm correct, 1.45bar is about 21.31lbs of boost. You may be experiencing knock and detonation. If you live in Colorado or high altitudes that's one thing, but on sea level, 21.31lbs of boost on 91 octane is way too much boost. I use 92 octane and 17lbs (1.15 bar) is the most I will go on 92. You better check your pistons to see if they are fried.

BTW, how does knock or detonation feel like???? Can you tell if you detonate? When I run 1.45 bar, the car pulls like hell and goes all the way to third pretty smoothly. I can do a full 1st to 3rd gear run and hit EGT's of 860c at 1.45bar. Is detonation related to EGT's and the number of timming i get? If so what are the numbers on the EGT's and how much timming would i show if Im knocking really bad and detonating? Thanks for the info again

 

[logic]

Here in the Chicago western suburbs, the best I'd been able to find was 93 octane at most stations. The other day, I noticed that a local Clark just down the street had one pump selling 100 octane race fuel. Expensive as hell, but nice to know it's there.

 

[Violater101]

Eeeks, 91 Octane and 21+ lbs of boost seems quite dangerous as Mistaspakles said. I bet if you did a log, you would notice a considerable amount of knock/timing being pulled back. What kind of EGT's are you seeing? Do they rise fast when u do a pull?

 

[larryd]

just out of curiosity, not sure if youve said this already or not but why only 91octane gas?

 

[ProjectGSX]

I would imagine he runs 91 octane because that is all he can get. California sucks like that - it's part of the reason I moved.

Anyways, as for tuning..

There is a limit to how much boost you can run without getting detonation, if intake temperatures and octane levels stay constant. The limit is not the boost level itself, but the temperature of the charge air after being compressed by the turbo. Since compressing the air heats it up, you can only compress it so far before reaching that heat threshold. Anything that lowers the temps of the air (eliminating boost leaks, water/nitrous/alcohol/propane injection, more efficient intercooling) will allow you to increase boost. Keep in mind that the efficiency of the turbo set up will affect how much the air is heated as it is compressed. Assuming you are not above that heat level:

Tuning for timing means tuning to make the ECU happy. This generally means you are more rich than necessary and are losing power. By tuning for timing, I mean aiming for 22+ timing with a 99ECU. Earlier 2G ECUs and definitely 1G ECUs award timing much easier and therefor "tuning for timing" would be more than 22 degrees of advance.

If you are tuning for power with a 99ECU, I aim for 18-20 degrees of advance. This puts you a bit more lean (but still rich) and certainly still with a safety zone in case temps change.

The bottom line is, you have to figure out what works for you. There are so many different variables to deal with, that no one can tell you what boost level you can run. Joe Blow over there might only be able to pull off 18psi with his 16G. Little does he know that he has a few minor boost leaks which is causing the turbo to spin faster to maintain that boost level, which is raising output temperatures to the same level your output temps are, at 20psi.

So put your datalogger to good use (I am assuming you have one) and let the dyno be your guide. Thanks to the popularity of the WRX, AWD dynos are popping up all over the place. Anyways, I hope this helps. I am certainly not an expert at this stuff.

 

[larryd]

wow.. that does stink.. i didnt know you can only get 91 out there.. I got good old 94 around the corner

 

[TURBOSPYDER]

Thanks for the info! Ill let you guys know what happens. Ill be tunning for sure this weekend and hope to finally get it down. I might just give up and hop on a dyno.

Larry,
The best street gas we have in Cali is 91 octane. Id have to go to Shell or Chevron for the good long lasting 91 octane. The cheaper gas stations like ARCO and the private companies gas suck big time and dont last long in the tank for some reason. Plus, price per gallon is about 1.95 - 2.00 for a gallon. It straight up sucks! Thats why my timing gets pulled even pig rich. I may just add octane booster every fill up.

 

[larryd]

damn that sucks.. I get 94 octane from sunaco out here for 1.74 a gallon

 

[pilotleston]

Here in my country we have 93, 96 and 98,5 octane gasolines; but after reading all that you say about yours I think that they must be measured differently, right? It can´t be posible that here ("world´s bottom" as we said to the geographical location of my country) we have better fuel than you do.

Well, I use this 98,5 octane fuel that I remembered now it says is 98,5 RON (I assumed that it is a method or norm for these stuff)

 

[jdmawd]

Originally posted by gst_spyder
91 octane , man Cali gas sucks, here in MD Sunoco has 94. With the mods you have i'd say it's time to put the Spyder on the dyno and tune it right since it doesn't look like it's going well on the streets since the 720's are making it harder to tune.

Mario

yup and on the eastern shore, around churchton. you can get 100 at sunoco 94 and a bottle of 108 octaine booster is what i use

 

[CornerHard]

Originally posted by pilotleston
Here in my country we have 93, 96 and 98,5 octane gasolines; but after reading all that you say about yours I think that they must be measured differently, right? It can´t be posible that here ("world´s bottom" as we said to the geographical location of my country) we have better fuel than you do.

Well, I use this 98,5 octane fuel that I remembered now it says is 98,5 RON (I assumed that it is a method or norm for these stuff)

You are correct - in North America we use (RON+MON)/2, which results in lower octane numbers for the same gas.

 

[pilotleston]

I found that MON is usually 8 to 10 units lower than RON, so yours 92 octane gasoline can be compared with a 96 or 97 octane of the one I have here, right?

And then I read that you have gas with more than 110 octane! wau! that would be great! (race gas, right?)

 

[silver91talon]

There are a lot of different opinions on "race gas", to me racegas is anything above 94 octane. The places around here have 100oct unleaded,110 leaded and 115leaded.

 

[pilotleston]

Why is there leaded 110 and 115?, is this octane level this high just because of the lead?

 

[RedTurboEclipse]

cali gas sucks! 91 octane with outrageous prices. darwin let me know how your car is doing.

 

[nano]

Lead helps reduce knock therefore encreasing octane. You can order up to 118 leaded fuel. Anything 110+ is freaken awsome in our cars if tuned properly.

21psi is a lot for 91 octane. A buddy of mine could run 20psi on he's big16G on 92 octane all through third with good timming on a cool engine, but when he got on fourth it would start knocking bad. As he's car car got hot after racing a lot it would start knocking even in third. He actually made the best power in third and fourth gear pulls at 17psi and .92 volts. Always tune for lower boost and richer then what you'd like because as the engine gets hot it's much more likely to knock specially at high speed rolls.