What lb/min are you flowing on pump & bigger turbos

[Kevin Jewer]

IIRC, your point was that TC outlet temps had to be the cause of your knock. Looking at that log above, air temps are the least of your worries. That is the worst timing curve I have ever seen. ~24 degrees around peak torque (Air/rev) is asking for a blown motor. That had to have put a ton of heat into everything. The 18-19 degrees up top wouldn't have been so bad if the curve started at ~10 degrees. The 2g curve will hit 10 by 5k, and 16-17 by redline. I've found that curve works very well on pump gas with larger setups. 14b and other small turbos can often get away with a little more.

I forgot what the point of all this was, so if I missed anyone's point, I appologize in advance.

 

[XakEp]

53 Lbs/min on 91 octane.

 

[Caithness]

I've heard of a theory that the weird decrease in 1g timing numbers after 6k might be related to timing belt stretch at higher rpm. The theory goes like this: the timing belt isn't completely rigid, and as the rpm rises it encounters more resistance from rotating the valvetrain. The drag from the valvetrain causes it to stretch a bit and by 7k rpm the effect is great enough to advance the timing ~2 degrees. Supposedly in the 2g cars there's some variable in the ecu that compensates for this, but in the less advanced 1g ecu the compensation was simply to reduce timing above 6k to make up for the belt stretch.

I can't remember where I heard this, but I think it was part of a discussion about calibrating AEM EMS and somebody's experience with flunky timing values until they changed a variable that compensated for timing belt stretch. I wish I could give a better description of exactly how the timing belt stretch advances the timing, but I'm too tired to think the mechanics through. All I can say right now is it was explained in a much more convincing and detailed fashion when I heard about it or I wouldn't have believed it myself ::.

This hasn't stopped me from smoothing out my timing curve and eliminating that bump at 6k, but I take a middle ground and avoid going crazy with the high rpm timing values. I stick with a plateau going with the same value I used at 6k, or maybe one degree more advance, and work with the theory that belt stretch is probably throwing in another degree or two. I do know that when I simply cranked the timing at high rpm while lowering the timing slightly at 6k I got knock up there.

 

[90AWDTalon]

I've heard of a theory that the weird decrease in 1g timing numbers after 6k might be related to timing belt stretch at higher rpm. The theory goes like this: the timing belt isn't completely rigid, and as the rpm rises it encounters more resistance from rotating the valvetrain. The drag from the valvetrain causes it to stretch a bit and by 7k rpm the effect is great enough to advance the timing ~2 degrees.

This isn't true, my timing is exaclty what I have it set at in my timing table thru out the entire rpm band. No stretching and no advance over what it is supposed to be.

 

[Kevin Jewer]

I could see the timing belt having some effect on cars running the 1g style CAS, but you wouldn't see it at the ECU. The ECU would still be trying to hit it's target, and the actual timing should end up being retardedin comparison, which is a good thing I guess. AEM does require adjustment of pickup delay comp on those cars, but people with 2Gs and EVOs using the crank trigger don't appear to see any drift. If you are tuning for the most timing you can run without knock this won't matter anyway since you would take up the difference by adding more timing. Just thinking out loud here...

 

[donmagicjuan]

This is an interesting phenomenon, but I agree that the effect would be a slight retard in timing rather than an advance. If the timing belt is stretching, then the crankshaft would be leading the CAS by a small amount. For timing controlled by the CAS, ignition would occur at a point later in the crankshaft rotation, i.e. actual timing would be retarded from the targeted value.

 

[Caithness]

Now that I think about this in a less-tired state I can't think of a way for timing belt stretch to advance the timing. If I ever remember who I heard that from or what thread I read that went into more detail, I'll post an update.

 

[Syndicate13]

Just an update. 47.5 lbs min at 24psi on the Green. 2G head FTW! I do have an Evo3 intake and cams though.

 

[NOSLO2PT0]

I must suck at tuning. 25psi, 2.0L FP3065, 45lb/min 11.58@119

 

[tstkl]

like I said, the only reason I was running the car with that timing curve was because it would be running insanely rich otherwise, and since then the problem has been fixed, reguardless. These were simply logs taken for the tuning process.

 

[zross1]

I must suck at tuning. 25psi, 2.0L FP3065, 45lb/min 11.58@119

Hey, I wouldn't say you suck at tuning. 11.5 @119 means you know what your doing. 45 lb/min is about right at 25 psi on the 3065. Throw in some race gas and crank up the boost and you'll see 50+ lb/min and a low 11 high 10 sec time slip. Don't worry about the lb/min. It's just a arbitrary number. 11.5 @ 119 is what matters.

 

[Kevin Jewer]

If measured properly airflow is absolutely not an arbitrary number! Unfortunately with the proliferation of uncalibrated MAFts it may seem that way at times though. I've seen incredible repeatability in airflow sensors, when setup properly, in all of my cars and setups.

 

[zross1]

If measured properly airflow is absolutely not an arbitrary number! Unfortunately with the proliferation of uncalibrated MAFts it may seem that way at times though. I've seen incredible repeatability in airflow sensors, when setup properly, in all of my cars and setups.

That's what I meant. I have a friend with a maft and a set-up that "should" be reading X lb/min in theory on X amount of boost that would be consistent with other similar set-up's. But because of his maft being uncalibrated his airflow reads much lower then to be expected.

I do still think that lb/min is just a number. Untill someone can tell me that they say 50lb/min and they go to the dyno and throw down around close to 500 hp I still think it's just a number. If someone has done aiflow #'s from dsmlink that are consistent with what a dyno actually says I'll retract my statement. Furthermore, who cares what kind of airflow your seeing if you put down some good numbers on a dyno or at the track. Those are the numbers that really matter. You may have seen incredible repeatability in airflow sensors in all your cars and set-up's but unless you went to the dyno to show that those cars were putting down similar hp those numbers are again arbitrary.

 

[90blacktsiawd]

That's what I meant. I have a friend with a maft and a set-up that "should" be reading X lb/min in theory on X amount of boost that would be consistent with other similar set-up's. But because of his maft being uncalibrated his airflow reads much lower then to be expected.

I do still think that lb/min is just a number. Untill someone can tell me that they say 50lb/min and they go to the dyno and throw down around close to 500 hp I still think it's just a number. If someone has done aiflow #'s from dsmlink that are consistent with what a dyno actually says I'll retract my statement. Furthermore, who cares what kind of airflow your seeing if you put down some good numbers on a dyno or at the track. Those are the numbers that really matter. You may have seen incredible repeatability in airflow sensors in all your cars and set-up's but unless you went to the dyno to show that those cars were putting down similar hp those numbers are again arbitrary.

Ok so I put down 346 awhp on the dyno and i was flowing 38.5 lbs/min for that dyno run. Sounds about right to me.

 

[MyBeatGSX]

Let the bench dynoing begin.

So what's the conversion, like ~1lb/min = 10hp?

 

[90blacktsiawd]

Let the bench dynoing begin.

So what's the conversion, like ~1lb/min = 10hp?

That's the general rule of thumb.

 

[MyBeatGSX]

Wheel or crank?

 

[zippyshoe]

Let the bench dynoing begin.

So what's the conversion, like ~1lb/min = 10hp?

Just wanted to add that this is 10 hp at the crank rather than at the wheels.

EDIT: Oops. I guess I answered your question before I saw your post, Tyler.

 

[zross1]

Ok so I put down 346 awhp on the dyno and i was flowing 38.5 lbs/min for that dyno run. Sounds about right to me.

I guess that's pretty close. I think when tuning it's good to use everything you can to get the best tune. Obviously, if your airflow numbers are out or wack from the "norm" and you have a calibrated maft you would take that into consideration and try to figure out what the proble is. But I'm not going to get worked up if I have low airflow numbers but the real world number (dyno and track #'s) are where they should be.

 

[donmagicjuan]

Lower airflow numbers for a given horsepower are actually a good thing. It means you have your ignition timing well adjusted.

 

[MyBeatGSX]

Lower airflow numbers for a given horsepower are actually a good thing. It means you have your ignition timing well adjusted.

And what about my just generally low airflow.

 

[90blacktsiawd]

And what about my just generally low airflow.

First thing i'd check for would be boost leaks. Then i'd want to be sure that whatever im getting the reading from isn't out of wack.

ZRoss i agree with you that airflow numbers shouldnt be the only thing you look at. But the more accurate information you have to work with the better off you'll be.

 

[Coup D E'Tat]

First thing i'd check for would be boost leaks. Then i'd want to be sure that whatever im getting the reading from isn't out of wack.

A boost leak will inflate airflow numbers, not make them appear lower.

 

[andymoraitis]

A boost leak will inflate airflow numbers, not make them appear lower.

That's true if you're using a GM MAF in draw through or a stock MAF since the metering is occuring before the leak. It is possible however to have lower numbers with a GM MAF in blow through if the leak is before it.

 

[90blacktsiawd]

A boost leak will inflate airflow numbers, not make them appear lower.

For most guys on here that's probably true. I'm thinkin of myself and my gm mas in my uicp.