467RWHP ATI, but with problems
467RWHP ATI, but with problems Just put the vette on the dyno to do some tuning to the PCM. Got it to put down 467/407 with an afr of approx 11.5-11.7:1. Looked pretty good, but on the street, I'm seeing knock pretty regular(.4-1.9deg.), starting at 3200-3400 and immediately lessening each consecutive frame, meaning that the pulled timing was effective.
My problem is with the low torque, although at a higher rpm, 407.5 @5100. Right now, I'm not able to run much tining in the midrange and actually have more pulled from here, than in the lower right area of the timing tables. Could not having headers be the problem? With headers, the gasses will be evacuated much easier. With them, would I be able to run more timing in the midrange?
Here is a line from edit, HO Timing Table, each column 1200-6400 @ .96 g/cyl as an example of my timing. All data below .96g/cyl is identical.
1200/1400 13deg.
1600 14deg.
1800 15deg.
2000/2200 18deg.
2400-4800 17deg.
5200+ 18deg.
Thanks,
Mike
My problem is with the low torque, although at a higher rpm, 407.5 @5100. Right now, I'm not able to run much tining in the midrange and actually have more pulled from here, than in the lower right area of the timing tables. Could not having headers be the problem? With headers, the gasses will be evacuated much easier. With them, would I be able to run more timing in the midrange?
Here is a line from edit, HO Timing Table, each column 1200-6400 @ .96 g/cyl as an example of my timing. All data below .96g/cyl is identical.
1200/1400 13deg.
1600 14deg.
1800 15deg.
2000/2200 18deg.
2400-4800 17deg.
5200+ 18deg.
Thanks,
Mike
TECH Addict
Joined: Nov 2001
Posts: 2,207
Likes: 0
From: College Station, Tx
Actually, headers will normally reduce the amount of timing you can run. With increase back-pressure you have more burned gasses retained in the the chamber (reduced charged quality) - this basically acts like an EGR setup. Your flame speed is reduced, and so you require more timing, no less.
That said you should see more torque with a good set of headers, though you may need to reduce the timing even more.
An easy check would be to throw in some hi-octane gas and play with the timing. If your torque picks up tremendously then you are definitely dynamic compression limited in your setup - if it doesn't then it's just the result of your pulley/cam combination. You do have a good bit of overlap with that camshaft, which is something you don't really need as much with a FI setup (since you should have higher manifold than exhaust pressure at WOT).
That said you should see more torque with a good set of headers, though you may need to reduce the timing even more.
An easy check would be to throw in some hi-octane gas and play with the timing. If your torque picks up tremendously then you are definitely dynamic compression limited in your setup - if it doesn't then it's just the result of your pulley/cam combination. You do have a good bit of overlap with that camshaft, which is something you don't really need as much with a FI setup (since you should have higher manifold than exhaust pressure at WOT).
Thanks Chris. I'll give it a shot next time I dyno. I have a can of 100 octane waiting to go in.
Myturbo
With the 4.1" pulley, rated by ATI at 5# on a stock motor, I'm seeing 6# at 62-6300rpms so I dont think I'm bleeding off that much.
May be a dumb question, but wouldn't a 224/230 114 have more overlap than a 224/224 112? I understand the benefit of longer exhaust duration, but I'm just thinking about overlap. Either way, I doubt I'll be pulling the cam. This things runs pretty good up top which is where it matters to me. Once I hit 4000+ this thing screams. And I just can justify pulling the cam to get some more grunt down low, when I only get to the track very infrequently. Also the lope+SC whine sounds pretty damn good
Although your average person thinks somethings broken when they hear a vett sound that way... got asked that a couple times.
Myturbo
With the 4.1" pulley, rated by ATI at 5# on a stock motor, I'm seeing 6# at 62-6300rpms so I dont think I'm bleeding off that much.
May be a dumb question, but wouldn't a 224/230 114 have more overlap than a 224/224 112? I understand the benefit of longer exhaust duration, but I'm just thinking about overlap. Either way, I doubt I'll be pulling the cam. This things runs pretty good up top which is where it matters to me. Once I hit 4000+ this thing screams. And I just can justify pulling the cam to get some more grunt down low, when I only get to the track very infrequently. Also the lope+SC whine sounds pretty damn good
Although your average person thinks somethings broken when they hear a vett sound that way... got asked that a couple times. 
TECH Senior Member
Joined: Nov 2001
Posts: 11,603
Likes: 0
From: Chi-Town, IL
You will pick up power with the headers, but its going to require a pulley change, the boost will probably drop to around 3-4psi w/your current setup..
When I went from 10.6:1 comp MTI heads on the stock shortblock to 9.3:1 comp TEA heads, my boost when from a max of 6psi to around 4psi....headers let the motor breath more, a head change w/that much compression difference will do a similar thing....
But if you run a smaller pulley, you can make more power w/less boost.....or get lower comp heads on top of that and run even more boost....
When I went from 10.6:1 comp MTI heads on the stock shortblock to 9.3:1 comp TEA heads, my boost when from a max of 6psi to around 4psi....headers let the motor breath more, a head change w/that much compression difference will do a similar thing....
But if you run a smaller pulley, you can make more power w/less boost.....or get lower comp heads on top of that and run even more boost....
Moderator
Joined: Nov 2001
Posts: 3,048
Likes: 12
From: Raleigh, NC
Your optimal dyno tune may be too lean for the street.
Without lessening timing, try adding some fuel in the RPM range where you have the most KR and see what that does for you. You will actually pick up power, even though you richened it up, if you are able to keep the timing rather than lose it to the KR demon.
Without lessening timing, try adding some fuel in the RPM range where you have the most KR and see what that does for you. You will actually pick up power, even though you richened it up, if you are able to keep the timing rather than lose it to the KR demon.
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Registered User
Joined: Jun 2002
Posts: 453
Likes: 0
From: Forced Induction Heaven
Some good tech info here but my old setup yielded different results.
My old ATI D1 setup yielded 610/545 RWHP/RWTQ
MODS
Forged 346 9.8:1 CR
SW LT Headers
Comp Xer 224/224 .581/.581 114lsa
You do have some overlap with your cam being it is on a 112 lsa...I actually used to use a split pattern on a 112 and got rid of it for the blower. I do not think it is your cam though. Split pattern might give you a little more hp but just for reference...my 224 cam vs. the LPE GT-3 cam made 30 more rwhp and 25 rwtq with everything the same except the cam! So the proof was in the back to back dyno runs.
I think your problem is in the tune. Something is not right...what is your AFR during the time you are getting Knock Retard???
My old ATI D1 setup yielded 610/545 RWHP/RWTQ
MODS
Forged 346 9.8:1 CR
SW LT Headers
Comp Xer 224/224 .581/.581 114lsa
You do have some overlap with your cam being it is on a 112 lsa...I actually used to use a split pattern on a 112 and got rid of it for the blower. I do not think it is your cam though. Split pattern might give you a little more hp but just for reference...my 224 cam vs. the LPE GT-3 cam made 30 more rwhp and 25 rwtq with everything the same except the cam! So the proof was in the back to back dyno runs.
I think your problem is in the tune. Something is not right...what is your AFR during the time you are getting Knock Retard???
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I just added another percent to the PE for the street, but ended up with knock in the same area. I'll add another when the rain stops here.
Knock on the street starts at 3200-3400. On the dyno, my AFR was 11.8:1 from approx 2600 to 4500 rpm and then richening up a little to 11.5:1 up to 6300. Blew the airbridge off on the last run and ended up crimping the one end when we tried to tighten it a little more(air leak) so we called it a day, before I got to even everything up.
The AFR was recorded with a tube inserted in the tailpipe.... Just an FYI. I'm not sure if this will have any effect on the measured afr, recording after the cats, or if it is as accurate at a sensor placed prior to the cats.
Bigbos,
That was sort of my plan for a winter project... do headers, racetronics and a 3.85 pulley, then retune it in spring.
Thanks,
Mike
Knock on the street starts at 3200-3400. On the dyno, my AFR was 11.8:1 from approx 2600 to 4500 rpm and then richening up a little to 11.5:1 up to 6300. Blew the airbridge off on the last run and ended up crimping the one end when we tried to tighten it a little more(air leak) so we called it a day, before I got to even everything up.
The AFR was recorded with a tube inserted in the tailpipe.... Just an FYI. I'm not sure if this will have any effect on the measured afr, recording after the cats, or if it is as accurate at a sensor placed prior to the cats.
Bigbos,
That was sort of my plan for a winter project... do headers, racetronics and a 3.85 pulley, then retune it in spring.
Thanks,
Mike
Registered User
Joined: Jun 2002
Posts: 453
Likes: 0
From: Forced Induction Heaven
You might possibly be picking up some false knock. Your AFR looks good....if you tune it about 11.5 on the dyno that should be no more than 12.5 on the street. Some tuners tune to close on the dyno and don't account for what happens on the street. Thats why I like the FAST and WB system..but I don't have time for that system..but it rules.
Check for false knock..your AFR looks good. Maybe you can desensitize the knock sensors a little and see what happens.
Check for false knock..your AFR looks good. Maybe you can desensitize the knock sensors a little and see what happens.
