Highest safe level of PSI on 91.
Originally Posted by coolguycooz
really? hits just under 20 psi and i get no knock on 91 octane. The only time i pick up knock is when the humidity is high or its hot.
Anybody elses toughts on octane booster?
Anybody elses toughts on octane booster?
Thread Starter
Evolving Member
Joined: Sep 2006
Posts: 368
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From: California
well before i roll out and do a pull ill hop on weather.com and check out the humidity for my area and temps. And generally ill get 1-2 counts when its over 80 F, the humidity aspect im not too sure about, but higher temp deffinetly cause me to pick up some knock vs doing pulls at 1 in the morning at 55-60 temps.
Originally Posted by coolguycooz
really? hits just under 20 psi and i get no knock on 91 octane. The only time i pick up knock is when the humidity is high or its hot.
Anybody elses toughts on octane booster?
Anybody elses toughts on octane booster?
Depends on the brand. some are junk, some work. I use Torco unleaded "concentrated race fuel" bought from their website. It actually does higher the octane depending on concentration. (it tells you how much to add on the bottle for desired octane) This stuff will put a orange color on you plugs and O2 sensors. But its harmless.
As for boost, here in Las Vegas the other night when the weather was 60*f, 95% humidity (it just rained all day) I was able to run 24psi peak tapering to 19psi at redline on 91oct, and 27psi peak with 24psi at redline on 94oct (mix of 100 and 91) with relitivly no knock. There were a few 1 counts and a couple 2 counts.
the only change I made to the ecu was to increase the boost limits to avoid boost cut (set everything to 265) otherwise it was a stock map in a stock 03 evoVIII with a hallman MBC. The next night at the racetrack, I ran strait 100 octane and 27psi peak with all 0's in the knock colum except for when I was on the 2 step. That gave me all kind of knock readings up to 15counts.
then the next day I ran my car down a clear hw in 5th gear from 80mph to 140mph without logging the run on 94oct with boost peaking at 27psi. This took me to 6k rpm when I felt the car hesitate for a instance. I believe either it switched into the lower octane maps or i was maxing the fuel pump out holding that much boost for that long. I wish I had my cable/lappy with me but oh well. I'll do it again soon.
the car did hold 25psi in 5th at 6k though. That supprised me.
Originally Posted by BoostN
Depends on the brand. some are junk, some work. I use Torco unleaded "concentrated race fuel" bought from their website. It actually does higher the octane depending on concentration. (it tells you how much to add on the bottle for desired octane) This stuff will put a orange color on you plugs and O2 sensors. But its harmless.
As for boost, here in Las Vegas the other night when the weather was 60*f, 95% humidity (it just rained all day) I was able to run 24psi peak tapering to 19psi at redline on 91oct, and 27psi peak with 24psi at redline on 94oct (mix of 100 and 91) with relitivly no knock. There were a few 1 counts and a couple 2 counts.
the only change I made to the ecu was to increase the boost limits to avoid boost cut (set everything to 265) otherwise it was a stock map in a stock 03 evoVIII with a hallman MBC. The next night at the racetrack, I ran strait 100 octane and 27psi peak with all 0's in the knock colum except for when I was on the 2 step. That gave me all kind of knock readings up to 15counts.
then the next day I ran my car down a clear hw in 5th gear from 80mph to 140mph without logging the run on 94oct with boost peaking at 27psi. This took me to 6k rpm when I felt the car hesitate for a instance. I believe either it switched into the lower octane maps or i was maxing the fuel pump out holding that much boost for that long. I wish I had my cable/lappy with me but oh well. I'll do it again soon. the car did hold 25psi in 5th at 6k though. That supprised me.
As for boost, here in Las Vegas the other night when the weather was 60*f, 95% humidity (it just rained all day) I was able to run 24psi peak tapering to 19psi at redline on 91oct, and 27psi peak with 24psi at redline on 94oct (mix of 100 and 91) with relitivly no knock. There were a few 1 counts and a couple 2 counts.
the only change I made to the ecu was to increase the boost limits to avoid boost cut (set everything to 265) otherwise it was a stock map in a stock 03 evoVIII with a hallman MBC. The next night at the racetrack, I ran strait 100 octane and 27psi peak with all 0's in the knock colum except for when I was on the 2 step. That gave me all kind of knock readings up to 15counts.
then the next day I ran my car down a clear hw in 5th gear from 80mph to 140mph without logging the run on 94oct with boost peaking at 27psi. This took me to 6k rpm when I felt the car hesitate for a instance. I believe either it switched into the lower octane maps or i was maxing the fuel pump out holding that much boost for that long. I wish I had my cable/lappy with me but oh well. I'll do it again soon.
the car did hold 25psi in 5th at 6k though. That supprised me.
Well, my best time in the 1/4 running 20-21psi before I had the cable to log (playing it safe) was 2/10th slower then my second run using the higher boost and trap speed was 2mph faster. However, I run it at 25peak now because somehow I just feel safer I guess and don't feel a difference from 25 to 27psi. .
I was beating Evo IX's with TBE at the track. Yet I've been driving awhile too so I can't blame it all on boost. My 60' times were 1-2 tenths quicker when I beat em. But to consistantly beat a IX with only a MBC made me feel pretty good.
As far as running Alky, he should be tuned for it with leaner AFR's and advanced timing. That makes it harder to run that much boost. I was simply seeing what the car would handle stock with only a MBC and the boost limits flashed out without knocking enough to switch to the lower octane maps.
and to directly answer your ?. Yes, I think 27 psi is out of the efficiancy range for a stock VIII. Also I think that weather conditions were ideal the night I logged that much boost.
I was beating Evo IX's with TBE at the track. Yet I've been driving awhile too so I can't blame it all on boost. My 60' times were 1-2 tenths quicker when I beat em. But to consistantly beat a IX with only a MBC made me feel pretty good.
As far as running Alky, he should be tuned for it with leaner AFR's and advanced timing. That makes it harder to run that much boost. I was simply seeing what the car would handle stock with only a MBC and the boost limits flashed out without knocking enough to switch to the lower octane maps.
and to directly answer your ?. Yes, I think 27 psi is out of the efficiancy range for a stock VIII. Also I think that weather conditions were ideal the night I logged that much boost.
Originally Posted by BoostN
I wish I had my cable/lappy with me but oh well. I'll do it again soon. the car did hold 25psi in 5th at 6k though. That supprised me.
the car did hold 25psi in 5th at 6k though. That supprised me. 
Originally Posted by BoostN
As for boost, here in Las Vegas the other night when the weather was 60*f, 95% humidity (it just rained all day) I was able to run 24psi peak tapering to 19psi at redline on 91oct, and 27psi peak with 24psi at redline on 94oct (mix of 100 and 91) with relitivly no knock. There were a few 1 counts and a couple 2 counts. the only change I made to the ecu was to increase the boost limits to avoid boost cut (set everything to 265) otherwise it was a stock map in a stock 03 evoVIII with a hallman MBC.
The next night at the racetrack, I ran strait 100 octane and 27psi peak with all 0's in the knock colum except for when I was on the 2 step. That gave me all kind of knock readings up to 15counts.
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Joined: Jul 2001
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From: Back and forth in the pacific
Originally Posted by Evo_Kid
We'll, different tuners use different methods from what I hear. Some will use more boost, less timing. Some retarded timing, with lean AFR. etc, etc.
If you had two tunes, say one at 23lbs & 1-2* timing at peak torque and one with 21lbs & 5-6* timing and they both are knock free, I guess you would just have to use a dyno to see what one make more torque.
If you had two tunes, say one at 23lbs & 1-2* timing at peak torque and one with 21lbs & 5-6* timing and they both are knock free, I guess you would just have to use a dyno to see what one make more torque.
Originally Posted by -=SPECTRE=-
what are you using to monitor psi?
Originally Posted by nj1266
The key here is your STOCK map. That is why you are not getting more than a few counts of knock here and there. But I would bet that your car's AFR is VERY rich. IMO, it is far better to lean the AFR to around 11-11.5:1 and lower the boost to around 22 psi on pump gas. IMO, your car would run more effeciently and might even produce more power with leaner AFR and lower boost. Ofcourse you will have to back off the timing in the mid-to-top end of the rpm.
Unlike my GT35r subie that just keeps building boost to 7.5k. I'm really not trying to build another 500+whp car. I'll be happy with 300-350whp since the evo is my daily driver. I also will let my wife race this car so we can keep her evo IX stock with that nice 100k warranty.
Originally Posted by Evo_Kid
It was an example.
That example is about where my timing is at 220 load 6* degrees peak torque, 240 @3* degrees 260 @ 2* 280@ 0 300@ -1*. When I gun it 1st gear and log no knock, 2nd gear log no knock, 3rd gear log no knock, these are all seperate runs same day 4th gear log 6 to 5 counts from 3800 to 4500 and then 4 counts to 5000 and after that up top all is well. My afr is at high 10's like 10.6 - 10.9. During these pulls I was at 1 degree greater on all those numbers above. I did an overlay of datalog lab though using the dyno graph function from a 4th gear pull from yesterday and today and about same temp outside and the graph today was over yesterdays graph in all points. Some how today though at peak torque I managed to hit 269 load point with error correction on. So that may have contributed to my knock also.
Man I am starting to think something is wrong with my, I got the mighty 93 octane here still cant get no timing lol, and my car doesnt seem to like being lean. By lean I mean like 11.3.
Originally Posted by mchuang
That example is about where my timing is at 220 load 6* degrees peak torque, 240 @3* degrees 260 @ 2* 280@ 0 300@ -1*. When I gun it 1st gear and log no knock, 2nd gear log no knock, 3rd gear log no knock, these are all seperate runs same day 4th gear log 6 to 5 counts from 3800 to 4500 and then 4 counts to 5000 and after that up top all is well. My afr is at high 10's like 10.6 - 10.9. During these pulls I was at 1 degree greater on all those numbers above. I did an overlay of datalog lab though using the dyno graph function from a 4th gear pull from yesterday and today and about same temp outside and the graph today was over yesterdays graph in all points. Some how today though at peak torque I managed to hit 269 load point with error correction on. So that may have contributed to my knock also.
rpmx100-----Load------Tim------AFR
35-37--------240ish-----4-2-----11.4-11.5
40-45--------220ish-----5-6------11.4-11.5
45-50--------220ish-----4-5------11.4-11.3
50-55--------low220s---6-7------11.3
55-60--------210-213---7-9------11.3-11.2
60-65--------205-196---9-12-----11.2
65-70--------195-180---11-16----11.2-11.1
70-75--------179-171---16-18----11.1-10.97
On some runs I do get knock counts of 3-1 range @ peak boost/torque and sometimes @ the top of the rpms range. On other runs no knock counts up top at all. The boost is set @ 21.xx and rarely goes to 22 psi. I run the car on 93-94 octane that I mix @ the pump.
The car consistently puts down about 300 whp and 280ish torque on the DLL dyno plot. Oddly, the most impressive dyno plots are the ones that have a bit of knock sum in them
