Is this a typical MR dyno?
Thread Starter
Race Director
Joined: Jun 2004
Posts: 13,961
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From: WI
Is this a typical MR dyno?
I took a baseline dyno recently and will be going back to play with timing and fuel ratio. The TQ curve is nice and flat but the HP curve is very peaky. Not bad for home ported heads though! It looks like shifting as high as possible is best, with the 2,000 RPM drop in gears.
The car at race weight is around 3,000 pounds. It is very fun to drive!
The car at race weight is around 3,000 pounds. It is very fun to drive!
Le Mans Master
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From: Akron Ohio
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Awesome torque curve! What cam are you running again?
I would think the short runner of the MR would generate a somewhat peaky HP curve.
I would think the short runner of the MR would generate a somewhat peaky HP curve.
Thread Starter
Race Director
Joined: Jun 2004
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From: WI
It appears to have a flatter tq curve than a HSR but a peakier hp curve? I was debating between the intakes and I guess I still am!
It's a very simple inexpensive build, I used the hot cam. My engine rebuild thread is here:
http://forums.corvetteforum.com/c4-t...ld-advice.html
The dyno operator thought I would pick up more power but I can't go to much more with 8.7 power ratio for TTA (could cut timing to limit hp though). It ran 12.02 at 116 last year and I've made changes since.
It's a very simple inexpensive build, I used the hot cam. My engine rebuild thread is here:
http://forums.corvetteforum.com/c4-t...ld-advice.html
The dyno operator thought I would pick up more power but I can't go to much more with 8.7 power ratio for TTA (could cut timing to limit hp though). It ran 12.02 at 116 last year and I've made changes since.
Le Mans Master
Joined: Oct 2007
Posts: 9,700
Likes: 3,469
From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
2024 C5 of the Year Winner - Modified
2023 C5 of the Year Finalist - Modified
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St. Jude Donor '09-'10-'11
It appears to have a flatter tq curve than a HSR but a peakier hp curve? I was debating between the intakes and I guess I still am!
It's a very simple inexpensive build, I used the hot cam. My engine rebuild thread is here:
http://forums.corvetteforum.com/c4-t...ld-advice.html
The dyno operator thought I would pick up more power but I can't go to much more with 8.7 power ratio for TTA (could cut timing to limit hp though). It ran 12.02 at 116 last year and I've made changes since.
It's a very simple inexpensive build, I used the hot cam. My engine rebuild thread is here:
http://forums.corvetteforum.com/c4-t...ld-advice.html
The dyno operator thought I would pick up more power but I can't go to much more with 8.7 power ratio for TTA (could cut timing to limit hp though). It ran 12.02 at 116 last year and I've made changes since.
You can actually go down to 8.3:1 ratio for TTA if you use a 275 or smaller tire. That is what I am hoping for, around 360-370 to the wheels and 3160 lbs.
Safety Car
Joined: Sep 2001
Posts: 4,157
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From: Glenbeulah Wi
Nice power, I don't think the power curve is peaky. The torque stays fairly flat until 5500 and then drops off quickly as the car runs out of air. You may be getting valve train control problems after 5500 that cause the torque to drop off that quickly.
Thread Starter
Race Director
Joined: Jun 2004
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From: WI
Funny you should mention that! Dyno Dave thought the pre-load was out on the lifters and I should adjust them. I did last weekend and most were a little loose. When I rebuilt the engine I did 1/2 a turn and had not readjusted them since. They either needed to be, or that was to little, or something else.
I am thinking A6's and 275's. I did like Matt's dyno and the small hp loss on my combo is either the intake or TPIS ports heads a little better than mine! Not sure where it will come up to with tweaking though.
I am thinking A6's and 275's. I did like Matt's dyno and the small hp loss on my combo is either the intake or TPIS ports heads a little better than mine! Not sure where it will come up to with tweaking though.
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Thread Starter
Race Director
Joined: Jun 2004
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From: WI
Thanks guys! I had no idea what to expect with the dyno curves. I now notice the tq decline, I hadn't before. I have 3/8" rocker studs if that is perhaps the issue. The numbers were very consistent across five runs.
Still working on tuning. Open loop is good, idle, PE, cruise. But closed loop goes lean, pulse width cap perhaps?
Still working on tuning. Open loop is good, idle, PE, cruise. But closed loop goes lean, pulse width cap perhaps?
Drifting
Joined: Mar 2009
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From: East Wenatchee (2hours from n e where) WA
Very Cool! Thanks for posting. I have always felt that I need to better understand what part of the tq/hp to use. The strongest tork at hook up comming off the turn is critical, even if it sacrifices power at the end of the straight. ie with the CT525 and 604 sealed engines the best lap times are on the chip well befor the point where the drivers are lifting. (my background is oval, Im just starting to learn about the righty lefty thing). You have a nice wide sweet spot to work with here, the part that concerns me is the eratic graph above 5900. Maby valve toss or lifter pump up? Crower or Comp might help out. It would be interesting to see a test with a little more spring. These springs are going to soften, if they are already barely getting the job done they could be a problum. More spring on the next pull will not interfear with any power tuning. I would be very interested in what the guys on the RR/AX board would say about shift points.
Burning Brakes
Joined: Aug 2000
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From: Albuquerque NM
with the MR intake, peak HP is 6500ish and ported heads+cam+exhaust should be 425ish HP when you let it run out. Though if your tunign with the stock ECU just fatten the fuel at 5500-5800 at rev limit at 6200ish. This is one of three reasons why i choose an aftermarket ECU.
Second, valve train is importamt. your signature didnt include Cam specs. That intake want lift, dwell, and duration. if you havent gotten a cam. Look (do not call) for a comp cam 224/224 .575" lift cam with good long duration at .200". look for XFI grinds.
Third, you need spring pressure to avoid valve float. aftermarket lifters can take 170-225 lbs seat load with up to 350ish open loads.
You are leaving about 1000 RPM on the table, and the increases in cam arent going to hurt low end torque.
Shape is accurate for short ram intake....flat torque curve.
Second, valve train is importamt. your signature didnt include Cam specs. That intake want lift, dwell, and duration. if you havent gotten a cam. Look (do not call) for a comp cam 224/224 .575" lift cam with good long duration at .200". look for XFI grinds.
Third, you need spring pressure to avoid valve float. aftermarket lifters can take 170-225 lbs seat load with up to 350ish open loads.
You are leaving about 1000 RPM on the table, and the increases in cam arent going to hurt low end torque.
Shape is accurate for short ram intake....flat torque curve.
Last edited by ZD1; Sep 3, 2012 at 02:44 AM.
Thread Starter
Race Director
Joined: Jun 2004
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From: WI
with the MR intake, peak HP is 6500ish and ported heads+cam+exhaust should be 425ish HP when you let it run out. Though if your tunign with the stock ECU just fatten the fuel at 5500-5800 at rev limit at 6200ish. This is one of three reasons why i choose an aftermarket ECU.
Second, valve train is importamt. your signature didnt include Cam specs. That intake want lift, dwell, and duration. if you havent gotten a cam. Look (do not call) for a comp cam 224/224 .575" lift cam with good long duration at .200". look for XFI grinds.
Third, you need spring pressure to avoid valve float. aftermarket lifters can take 170-225 lbs seat load with up to 350ish open loads.
You are leaving about 1000 RPM on the table, and the increases in cam arent going to hurt low end torque.
Shape is accurate for short ram intake....flat torque curve.
Second, valve train is importamt. your signature didnt include Cam specs. That intake want lift, dwell, and duration. if you havent gotten a cam. Look (do not call) for a comp cam 224/224 .575" lift cam with good long duration at .200". look for XFI grinds.
Third, you need spring pressure to avoid valve float. aftermarket lifters can take 170-225 lbs seat load with up to 350ish open loads.
You are leaving about 1000 RPM on the table, and the increases in cam arent going to hurt low end torque.
Shape is accurate for short ram intake....flat torque curve.
I am not sure what springs are in there though, they are not stock. I am tuning the stock ECU and the rev limit is set to 6383.
Le Mans Master
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From: Australia
Le Mans Master
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From: Akron Ohio
2025 Corvette of the Year Finalist - Modified
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I would like the extra RPM! I have the hot cam with 1.6 roller rockers, IIRC LS1 lifters, and when we built the engine it went on the cam docker. Here's a pic:
I am not sure what springs are in there though, they are not stock. I am tuning the stock ECU and the rev limit is set to 6383.
I am not sure what springs are in there though, they are not stock. I am tuning the stock ECU and the rev limit is set to 6383.
221/228 @0.050 duration
275/284 Adv
142/146 @0.200 durtion
111 LCA
107 ICL
I have nicknamed it "The Hotter Hot Cam" since they are kinda close but different in a lot of ways
Team Owner
Joined: Mar 2000
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From: Boston, MA
Agreed, he has a bottleneck in there. That HP dropping off at ~5500 is more in line with what I'd expect to see from a SuperRam setup than a MiniRam. Regardless it's a good amount of smooth power that most folks wouldn't expect from an 80s smog vette. 
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From: Fredonia WI
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