Knock above 20psi on scm61

[jkimes]

I've been told that lots of 60-1 guys are able to run 24psi on pump, but even after tweaking my setings in dsmlink for weeks (on long straight country roads to try and avoid cops ) I still can't seem to boost any higher than 20psi without getting lots of knock. Could this just be crappy fuel, or am I running out? Im running a walbro 255hp fuel pump, with stock fuel pressure regulator and stock wiring. I've considered rewiring the pump, but I'm afraid that I may overrun the stock FPR if I do.

 

[1fast97gsx]

could be crappy fuel, crappy tuning, or a crappy intercooler causing it to heatsoak. 22 psi should be doable if not more with proper tuning.

 

[jkimes]

could be crappy fuel, crappy tuning, or a crappy intercooler causing it to heatsoak. 22 psi should be doable if not more with proper tuning.

Do you think I could be running out of fuel with the non-rewired 255hp and 880cc injectors, or is poor fuel quality more likely? If someone could elaborate a little more about the crappy tuning part it would probably help me out. I've tweaked my A/F ratio throughout the powerband to as close to 11:1 as possible, however around 4000 rpms the boost spikes really quicky with this turbo and occasionally leans out to 14:1 for a few seconds until boost stabilizes. I've tried to adjust my fuel map to compensate for this problem but the knock just won't go away even if I yank timing more than two degrees. I have a pretty large front mount (although it is of the ebay variety) I've never heard anyone say anything negative about this intercooler model.

 

[ACKERSON]

When I rewired my pump it made a huge difference with my scm60. I was running 24 psi on pump gas with no knock. I had about 7 or 8 volts at the pump before the rewire and 13 or so after the rewire. Thats a HUGE increase in flow with the rewire. I'm not saying that will fix your problems but it helped me out a lot

 

[desolateboosted]

Yeah mainly the reason why you can't boost so high is because of shitty ass fuel. You either have to richen it up so much to keep the knock low or lower the boost. On pump I can do 24psi with about 0 knock but it doesn't feel fast at all. All the fuel is robbing most of the power. When I switch to race gas and lean it out 15% on the same 24psi setting it pulls mad.

 

[DSMTalonAWD51]

get an afpr. youre most likely getting non-linear fuel pressure and its making it hard to control your fuel

 

[evil_eagle]

What octane is your pump gas? if your talking about like 91 octane then it is a battle to keep it from getting some kind of knock. Most of us don't tune for 0 counts, I have tried that with crappy results, some people perfer more timing then boost, others like more boost then timing. It's a toss up.

more boost = less timing= hotter EGT's= hotter motor temps.
less boost = more timing = more torque= lower EGT's= more efficient running motor=cooler running motor.

Honestly I would perfer less boost and more timing on pump gas, but that just me, you can feal torque by the butt-o-meter more then you can HP.

Pump gas can only handle so much compression, remember here, boost raises compression. You are 8.5~1 compression, while others that run 24lbs maybe have 1g's and they are 7.8~1 compression, lower the compression it is the more you can get away with the boost.

Just things to keep in mind, don't try and shoot for what other people are tunning for, tune for what your car likes the most, check plugs often while tuning, plugs tell you everything that is going on with the motor, check logs back to back, compare each log and go from there.

Every car is different, you put the same exact mods on another dsm, same year and all, same mods, and I put money on it it will run completely different.

Smaller turbos you can get away with more timing advance, bigger turbos such as yours you need to back off the timing like 1.5-2 degrees.

Good luck with what your doing, but just tune for what your car likes the most, it's not allways necessary to have to run more boost to get power out of the car. I have learned that along time ago, more boost does not allways mean more power, I ran 10.85 @132mph with 26lbs of boost on the fp3065 turbo, so it's not allways about running alot of boost, it's how you tune it.

 

[RavenX]

What octane is your pump gas? if your talking about like 91 octane then it is a battle to keep it from getting some kind of knock. Most of us don't tune for 0 counts, I have tried that with crappy results, some people perfer more timing then boost, others like more boost then timing. It's a toss up.

more boost = less timing= hotter EGT's= hotter motor temps.
less boost = more timing = more torque= lower EGT's= more efficient running motor=cooler running motor.

Honestly I would perfer less boost and more timing on pump gas, but that just me, you can feal torque by the butt-o-meter more then you can HP.

Pump gas can only handle so much compression, remember here, boost raises compression. You are 8.5~1 compression, while others that run 24lbs maybe have 1g's and they are 7.8~1 compression, lower the compression it is the more you can get away with the boost.

Just things to keep in mind, don't try and shoot for what other people are tunning for, tune for what your car likes the most, check plugs often while tuning, plugs tell you everything that is going on with the motor, check logs back to back, compare each log and go from there.

Every car is different, you put the same exact mods on another dsm, same year and all, same mods, and I put money on it it will run completely different.

Smaller turbos you can get away with more timing advance, bigger turbos such as yours you need to back off the timing like 1.5-2 degrees.

Good luck with what your doing, but just tune for what your car likes the most, it's not allways necessary to have to run more boost to get power out of the car. I have learned that along time ago, more boost does not allways mean more power, I ran 10.85 @132mph with 26lbs of boost on the fp3065 turbo, so it's not allways about running alot of boost, it's how you tune it.

Couldn't agree with you more. Also you don't need to shoot for 11.0:1 you can also go for 10.8:1 as that is still pretty good. Other than that evil eagle pretty much covered eveything. You can always post a log for us dsmlink guys to see it will give us more of a idea on what your car is doing

 

[jkimes]

Thanks alot for the advice, Im going to rewire my fuel pump tonight and try and tune for lower boost with more timing on 93 octane. Has anyone had problems with the stock FPR after rewiring a walbro 255hp?

 

[RavenX]

Thanks alot for the advice, Im going to rewire my fuel pump tonight and try and tune for lower boost with more timing on 93 octane. Has anyone had problems with the stock FPR after rewiring a walbro 255hp?

Your going to overun the fpr thats all i have to say

 

[92tealTSI]

you are running a 255hp pump and 880's but have a stock FPR?!? you should definately get a 1:1 rising rate FPR like the aeromotive peice and Ill bet that will take care of your problems.

 

[1fast97gsx]

evil eagle's post was very helpful. I'm in a similar situation right now with the same turbo. I was trying to run 22 - 23 psi on a 9:1 motor and even with a fairly rich tune I was knocking in higher gears and the power just wasn't there. I was only trapping around 87 mph in the 1/8th mile and only pulling 12.4s and 12.5s. I turned the boost down to just under 20 and leaned it out a little and did another run. Needless to say my 1/8th mile trap speed went up to 91 but I missed 4th gear so I still only ended up with a 12.4 slip. This was with a 1.9 60 foot and missing 4th gear though at only 20 psi. Before I was at 23 psi hitting all gears and getting 1.8 60 foots and my times were slower and I was trapping lower. Just lower your base timing 1 - 1.5 degrees and run about 20 psi. With a decent tune it will haul ass and you will have no knock.

As far as fpr overrun ... isn't this only an issue at idle? I've been told numerous times the reason for upgrading fprs is so at idle the pressure can be turned down, however at wot it won't have much of an effect. I'm also on a stock fpr ( 1g fpr and rail ) and don't see the need to upgrade ... unless my thinking is totally wrong?

 

[RavenX]

Also so some people know you can always gap your plugs to .24 instead of .28. From what i have heard it seems to help when running high boost. I will be trying this soon as i have problems tuning above 20psi wo well see if its true or not

 

[1fast97gsx]

I always thought .028 wasn't neccesary until 20+ psi anyways? If a smaller gap is needed for higher boost numbers I will give that a shot as well.

 

[Staytuned]

.24 seems a little tight for 20 psi of boost doesn't it? I have mine gapped to .28 and that seems so small.

 

[1fast97gsx]

This is what rre suggests:

Colder plugs will retain less heat between combustion cycles, thereby reducing the tendency toward damaging detonation elevated boost levels. Spark plug gap should be set at .030" for up to 16psi boost. Set at .028" for 17psi and up.

 

[Burnett03]

As far as fpr overrun ... isn't this only an issue at idle? I've been told numerous times the reason for upgrading fprs is so at idle the pressure can be turned down, however at wot it won't have much of an effect. I'm also on a stock fpr ( 1g fpr and rail ) and don't see the need to upgrade ... unless my thinking is totally wrong?

You are totally wrong. It overuns the base pressure and from there you are always out of wack. If your base pressure is to high with the overrun regulator (lets say 45psi) And you are running 15 psi you are at 50psi right there.. It makes the fuel curve non linear. I cant believe you are on 850cc injectors, 255 pump and no regulator, shame shame...

 

[evil_eagle]

evil eagle's post was very helpful. I'm in a similar situation right now with the same turbo. I was trying to run 22 - 23 psi on a 9:1 motor and even with a fairly rich tune I was knocking in higher gears and the power just wasn't there. I was only trapping around 87 mph in the 1/8th mile and only pulling 12.4s and 12.5s. I turned the boost down to just under 20 and leaned it out a little and did another run. Needless to say my 1/8th mile trap speed went up to 91 but I missed 4th gear so I still only ended up with a 12.4 slip. This was with a 1.9 60 foot and missing 4th gear though at only 20 psi. Before I was at 23 psi hitting all gears and getting 1.8 60 foots and my times were slower and I was trapping lower. Just lower your base timing 1 - 1.5 degrees and run about 20 psi. With a decent tune it will haul ass and you will have no knock.

As far as fpr overrun ... isn't this only an issue at idle? I've been told numerous times the reason for upgrading fprs is so at idle the pressure can be turned down, however at wot it won't have much of an effect. I'm also on a stock fpr ( 1g fpr and rail ) and don't see the need to upgrade ... unless my thinking is totally wrong?

Glad it worked out for you, see what I mean? More boost does not allways mean more power, tune some more at lower boost and see what you can do with it. Good luck man, glad to hear it helped you out..

-Jake M

 

[Violater101]

JKimes: What kind of timing were you trying to run on pumpgas with that boost level? I posted this before in other threads, but with the dsmlink, I've found that I can't run more than 14 (timing retarded by 2) to 16 deg (stock timing) @20psi on 93 octane (but this was in the summer months and 99F heat). Most people with 2g's don't realize that although they are getting advanced timing with their afc setup, odds are they are still knocking despite a timing curve that continues to rise. At these kind of boost levels, your in (or should be in) the high airflow map which means that the max timing your going to get without adjusting the timing sliders is 16. I don't even dare to try to run that kind of boost personally on pumpgas...just too many variables that could go wrong and motor goes boom.

 

[danl]

Try reducing cooling temperatures. If you can get coolant temps to 180 degrees as compared to 195 degrees you will increase the detonation threshold significantly. Also run much colder spark plugs. Two heat ranges colder than stock is about where you should be with that turbo.

If you can tune for 5 counts of knock with the periodic spike to 10 on pump gas your about as maxed out as you can be. You can knock much more and make a little more power, but most people don't like doing that to their motors.

 

[ltho98]

Whoa, before we even think about saying this or that.. are you sure you're not overrunning your MAF? I've seen a 50 trim overrun a 2G mas at 20psi in the upper rpm range.

A 60-1 would defenitely overrun if it followed suit.

 

[RavenX]

Whoa, before we even think about saying this or that.. are you sure you're not overrunning your MAF? I've seen a 50 trim overrun a 2G mas at 20psi in the upper rpm range.

A 60-1 would defenitely overrun if it followed suit.

Thats pretty interesting. I thought the limit for the 2g Mas for around 2500hz and 500hp or something like that? Damn am gonna have to log Mafraw now to see where i am at

 

[ltho98]

You could also just look at your afc and watch it peg.

 

[jkimes]

What model NGK's should I be using? Also, how do I tell if Im maxing out my MAF?

 

[ltho98]

I would run an NGK BPR8ES for a good margin of safety.

You can tell if you're overrunning your MAF when you look at the input frequency from the MAF on your AFC, emanage, logger, or whatever, and when you keep accelerating and you see the values not go any higher.