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#1 |
![]() Join Date: Jul 2012
Location: Allentown, PA
Posts: 309
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Had a good day at the dyno with my '93. Questions frequently come up here about what various mods can do for our motors. Thought I'd post a comparison of my 2009 dyno results and today's. Mods as of '09 included siamesed plenum and injector housings, 63 mm throttle body, and B&B exhaust (stock manifolds and cats). Since then the heads have been ported, cams have been swapped, and SW headers (no cats) and mufflers have been added. Picked up 80 RWHP and 33 ft. lbs. torque. Using a 15% driveline loss, HP at the crank is now 558. Pretty amazing for a stock short block. HP/liter is almost as much as a supercharged LS9! Gotta love these motors!
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'95 ZR-1, aqua/gray, #167 368 LPE/Haibeck, Web cams, Stainless Works headers, B&B Fusion exhaust, 18" Fikse wheels, Alcon brakes, lowered. 491 SAE RWHP. |
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#2 |
Join Date: Jun 2013
Location: Toronto
Posts: 782
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Awesome numbers !
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#3 |
![]() Join Date: Jul 2012
Location: Allentown, PA
Posts: 309
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Thanks! Intakes are 0.435"/238 deg. Exhausts are 0.432"/220 deg.
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'95 ZR-1, aqua/gray, #167 368 LPE/Haibeck, Web cams, Stainless Works headers, B&B Fusion exhaust, 18" Fikse wheels, Alcon brakes, lowered. 491 SAE RWHP. |
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#4 | |
Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,696
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[SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX |
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#5 |
![]() Join Date: Jun 2005
Location: CenCoast California
Posts: 899
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Actually, your engine is making more than 558. The parsitic loss number for C4 manual powertrains which GM gave me an number of years ago was 18%. If you use that, you're making 578, but, either way that's impressive from a 350 and that's the good news.
The bad news is that, in reading the small print at the bottom of that .pdf, I noted that the data is "[ CF: Uncorrected 1.00 ]" That means the numbers are raw data uncorrected for any atmospheric conditions present at the time the tests were run. Any comparison between "before" and "after" power and torque numbers is not credible. Why not go back to the dyno operator and ask him/her to provide SAE corrected data for both tests? Lastly, looking at the AFR data at the bottom of the sheet, Dennis you need to be careful as I think you've got that engine running lean at WOT. If it was me, I'd be looking for someone to put a little more fuel to that engine...get that AFR so it's averages 12.5:1, if you're using non-blended fuel, and 12.2:1 if you're using E10 gas.
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Hib Halverson Technical Writer former owner 95 VIN 0140 current owner 19 VIN 1878 Last edited by Hib Halverson; 11-12-2017 at 02:55 PM. |
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#6 |
![]() Join Date: Jul 2012
Location: Allentown, PA
Posts: 309
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Thanks Hib!
Appreciate your comments! Yes, the numbers as shown are uncorrected. There are several different correction factors that can be applied, SAE being the most conservative. And. But I don't trust any of them to accurately adjust for changes in ambient conditions, especially when you're testing in conditions that are significantly different from Standard. The only truly valid comparisons are between tests on the same Dyno on the same day and even the same time of day. I threw out the comparison just to give those interested in similar mods an idea of what to expect. Individual results will vary, as they say, and by a lot! Re the AFR, I was shooting for an average of 12.7 which is where power and torque peaked across the rpm range. I made a few more tweaks after this last run to bring the high spots down. I have an A pillar mounted AFR gauge and keep an eye on it all the time. Have never had an issue or seen any evidence of same (I inspect the plugs and piston tops and Marc was most recently in the motor and reported no problems) running around 12.7. If you're aware of anyone that's run into problems running there, please pass it on. Timing was also optimized across most of the range (I didn't spend any time messing with it below 3000 RPM). The knock sensor kicked in a few times as I was looking for the sweet spots and was backed off accordingly. Bottom line is the car runs great and never ceases to thrill me, even after 25 years of ownership! There's good reason why we're all so passionate about these cars!
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'95 ZR-1, aqua/gray, #167 368 LPE/Haibeck, Web cams, Stainless Works headers, B&B Fusion exhaust, 18" Fikse wheels, Alcon brakes, lowered. 491 SAE RWHP. |
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#7 |
![]() Join Date: Jul 2017
Location: West Chester, PA
Posts: 378
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Cool post. I dig this kind of tech stuff. Thanks!
Sent from my SM-N920V using ZR-1 Net Registry mobile app
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#8 | |
Join Date: Aug 2005
Location: Fishers, IN
Posts: 809
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My personal experience doesn't back up the fixed 18% driveline loss. I believe that may have been relevant for a 300hp LT-1, with a 55 hp loss through the driveline (18%). In my experience, a 703 BHP (STP corrected), 669 bhp (SAE 1367) engine horsepower made 638 SAE 1367 rwhp on a dynojet. The engine dyno numbers were "green", the engine was more broken in by the time of the chassis dyno. The chassis dyno was confirmed and consistent over three sessions and two different dynojets. I was also surprised by the losses, given the urban legends about 15 or 18% and so on. YMMV, Todd
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Todd ____________________________________ *** our email address has changed! info@pepmeierengines.com pepmeierengines.com Friend us on Facebook too: www.facebook.com/profile.php?id=100011443683384 Pepmeier Engine Development |
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#9 |
![]() Join Date: Aug 2015
Location: Magnolia, Texas
Posts: 884
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My engine was running AFR's in the 12.2 range. My understanding from Marc's writeup and my own tuning experience is this was pretty fat. Marc recommends between 12.9 and 13.1 I believe. I changed my tune to lock in at 12.9 at WOT to 7000 rpm. Coupled with a colder plug and .050 plug gap, the engine runs like a scalded dog and purrs at idle. My experience says Marc is on point. 12.9 to 13.1 AFR is a sweet spot.
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#10 |
![]() Join Date: Jul 2012
Location: Allentown, PA
Posts: 309
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So, Todd, your results suggest that driveline loss is closer to a fixed number (approximately 50 for our cars?) rather than a percentage of FWHP. Correct? Awesome numbers, btw!
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'95 ZR-1, aqua/gray, #167 368 LPE/Haibeck, Web cams, Stainless Works headers, B&B Fusion exhaust, 18" Fikse wheels, Alcon brakes, lowered. 491 SAE RWHP. |
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