H/C/I LT1 dyno results
10-14-2013, 04:03 PM
#1
TECH Regular
Thread Starter
H/C/I LT1 dyno results Finally got the car back together and on the rollers.
Setup consists of:
1997 Z28 6 speed, factory 10 bolt rear with 3.42s, aluminum driveshaft.
-stock 109k mile shortblock
-Ai 200cc heads and 228 degree HR camshaft
-Ai CNC ported LT1 intake manifold with corrected geometry
-58mm Edelbrock throttle body, KN CAI, stock MAF
-SVO red top 30s
-Hooker LTs, no-name O/R Y pipe, Borla catback
-OBD1 conversion
I'm happy with the numbers and the way the car drives, but they are 15-25 shy of what I've seen some others achieve with setups similar to this one. I think the exhaust is holding it back that last little bit due to my Y-pipe being rather restrictive (it shrinks to about 2.5" diameter at the back where it plugs into the intermediate pipe).
When I do a clutch change in a few months I'll probably just swap out the Y with a better one and maybe put in a cutout.
Setup consists of:
1997 Z28 6 speed, factory 10 bolt rear with 3.42s, aluminum driveshaft.
-stock 109k mile shortblock
-Ai 200cc heads and 228 degree HR camshaft
-Ai CNC ported LT1 intake manifold with corrected geometry
-58mm Edelbrock throttle body, KN CAI, stock MAF
-SVO red top 30s
-Hooker LTs, no-name O/R Y pipe, Borla catback
-OBD1 conversion
I'm happy with the numbers and the way the car drives, but they are 15-25 shy of what I've seen some others achieve with setups similar to this one. I think the exhaust is holding it back that last little bit due to my Y-pipe being rather restrictive (it shrinks to about 2.5" diameter at the back where it plugs into the intermediate pipe).
When I do a clutch change in a few months I'll probably just swap out the Y with a better one and maybe put in a cutout.
10-14-2013, 05:10 PM
#3
It is peaking early from what I have seen of that cam in other cars including myown.
If making that through muffler and choked down to 2.5" single at one point you are doing just fine and more is left in the exhaust.
I ran dual 3" through mufflers than dual 2.5 over the axle and to the bumper. True dual was stock on the LT1 b-body though so it is a LOT easier for the b-bodies than f-bodies.
If making that through muffler and choked down to 2.5" single at one point you are doing just fine and more is left in the exhaust.
I ran dual 3" through mufflers than dual 2.5 over the axle and to the bumper. True dual was stock on the LT1 b-body though so it is a LOT easier for the b-bodies than f-bodies.
10-14-2013, 08:28 PM
#4
Very good.
Yes, you have a bunch left in the exhaust.
I run the same heads and cam with a stock intake manifold. Mine peaked at 6400 rpm with small Tri-Y headers and open collectors, and holds power to the 7100 rpm cutoff.
I also think that flat area in the torque curve between 3500 and 4600 shows you may have a little left on the table. That peak torque at 4700 is very good, but you may see it peak even higher than that a few hundred rpm lower by tweaking the tune in the 3500 to 4600 range. That heads/cam combo is not a peaky setup; the torque curve should have an overall rounded shape.
What's your CR? head cc? Are you running the Impala gasket?
Congrats on a well-executed build
Yes, you have a bunch left in the exhaust.
I run the same heads and cam with a stock intake manifold. Mine peaked at 6400 rpm with small Tri-Y headers and open collectors, and holds power to the 7100 rpm cutoff.
I also think that flat area in the torque curve between 3500 and 4600 shows you may have a little left on the table. That peak torque at 4700 is very good, but you may see it peak even higher than that a few hundred rpm lower by tweaking the tune in the 3500 to 4600 range. That heads/cam combo is not a peaky setup; the torque curve should have an overall rounded shape.
What's your CR? head cc? Are you running the Impala gasket?
Congrats on a well-executed build
10-14-2013, 10:48 PM
#5
TECH Regular
Thread Starter
56.5cc chambers, .026 gasket. I never did the math, but I figured the compression is around 11.2 or so.
The problem with the current y-pipe I'm running is the fact that it's a "male end" at the rear where it plugs into the intermediate pipe, so it's neccesarily smaller in diameter at that point. Most others I've seen are "female end" where the intermediate pipe plugs into them and hence there's no choke point where one pipe narrows to fit inside another.
I reckon it was not a problem with my old setup (stock heads and 224* cam making ~350rw), but with this new setup it's obviously a restriction.
I'm just going to drive the car for now, but a new clutch is coming this winter and I'll take the opportunity to do something about the exhaust while the car is on the rack at that time.
Not exactly sure what I'd do about an alternate exhaust setup. It's already not exactly quiet in any case and it's horrifically loud with the Borla plates removed. I know I'd rather not have true duals just for ground clearance reasons.
The problem with the current y-pipe I'm running is the fact that it's a "male end" at the rear where it plugs into the intermediate pipe, so it's neccesarily smaller in diameter at that point. Most others I've seen are "female end" where the intermediate pipe plugs into them and hence there's no choke point where one pipe narrows to fit inside another.
I reckon it was not a problem with my old setup (stock heads and 224* cam making ~350rw), but with this new setup it's obviously a restriction.
I'm just going to drive the car for now, but a new clutch is coming this winter and I'll take the opportunity to do something about the exhaust while the car is on the rack at that time.
Not exactly sure what I'd do about an alternate exhaust setup. It's already not exactly quiet in any case and it's horrifically loud with the Borla plates removed. I know I'd rather not have true duals just for ground clearance reasons.
10-15-2013, 06:00 AM
#6
I don't know if I missed it but who did the tune? Your cr is closer to 11:1, bowtienut is at 12:1 with an 0.015 gasket and heads milled 0.010, but I don't think that is why his pulled longer. Can't remember the other guy with that same setups name but he made I think 428 rwhp, your close.
10-15-2013, 07:10 AM
#7
With my AI 200cc setup I gained around 17-19 ft/lbs and HP thought the entire RPM range by just opening the cutout. My exhaust is JetHot long tubes with a custom y pipe that is dual 3" flowing into a flowmaster merge then into a Magnaflow 3" catback which is obviously a restriction if I gained that much by an open cutout.
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10-15-2013, 10:10 AM
#8
TECH Regular
Thread Starter
I don't know if I missed it but who did the tune? Your cr is closer to 11:1, bowtienut is at 12:1 with an 0.015 gasket and heads milled 0.010, but I don't think that is why his pulled longer. Can't remember the other guy with that same setups name but he made I think 428 rwhp, your close.
