Guest Tyler Posted July 23, 2006 Share Posted July 23, 2006 Hey folks, First post here. I've got a 260Z tubbed and details will follow... Good to meet you. Maybe someone here can help me with some math... Had a lot of fun with the dyno at Car Craft Summer Nationals yesterday. I learned a lot. Like for instance, running a car on the chassis dyno is a far cry from just the engine dyno. The E85 SBC is a 13:1 motor (406ci) that made a best pull of 590hp at 6800 RPM 530 lb/ft at 4900 RPM up at R&R on the engine dyno. On a bad pull (way out of tune or some other more significant issue) we'd see numbers like 560 and 500. On the chassis dyno we only got 468.8 hp and 488.2 lb/ft. I can't say for sure what RPMs these are at since the the dyno print out sheet claims the engine power curve runs from peak torque at 3600 to peak horsepower at 8000. Of course these can't be right. I know they didn't run it past 6800 because they asked me where to cut it off and that's what I told them assuming it couldn't make more power in the car farther up than it did under ideal cirmcumstances on an engine dyno. From the looks of the graph, it seems like I should have let them spin it up higher since the curve is still climbing at the end. Weird. I wonder if he pulled out early just to be safe. Anyway, when I asked the driver about the difference between numbers from one dyno to the other he asked me a series of questions: 1. What tranny? 2. What stall? Since I was running a TH400 and a 5000 stall he said that totally explains the screwed up RPM numbers on the dyno graph. And he didn't seem suprised that the engine performed they way it did under these real world conditions. Even after I told him what we did on the engine dyno. He said he's seen 750hp engines become 500hp engines going from engine dyno to chassis. That seemed crazy to me. On the engine dyno there is no drag or loss from the following compontents that are on the car as it sits: 1. mechanical piston style fuel pump (1-2 hp?) 2. full dual exhaust system 3" all the way back to superflow 40s (20hp?) 3. stock waterpump and alternator with march performance ratio pulleys (10-20?) 4. the load of the tranny, 5000 stall convertor, and dana 44 etc. has to account for the rest. That's like 80+ hp loss through the drive train! Is that right? The engine didn't behave like there was something really screwed up on it. Also, I was shocked that a high hp engine would look like a torque motor when viewed through the eyes of a chassis dyno. Thoughts? Anyone else experience something like this? Quote Link to comment Share on other sites More sharing options...
COZY Z COLE Posted July 24, 2006 Share Posted July 24, 2006 Anyway' date=' when I asked the driver about the difference between numbers from one dyno to the other he asked me a series of questions: 1. What tranny? 2. What stall? Since I was running a TH400 and a 5000 stall he said that totally explains the screwed up RPM numbers on the dyno graph. And he didn't seem suprised that the engine performed they way it did under these real world conditions. Even after I told him what we did on the engine dyno. He said he's seen 750hp engines become 500hp engines going from engine dyno to chassis. That seemed crazy to me. On the engine dyno there is no drag or loss from the following compontents that are on the car as it sits: 1. mechanical piston style fuel pump (1-2 hp?) 2. full dual exhaust system 3" all the way back to superflow 40s (20hp?) 3. stock waterpump and alternator with march performance ratio pulleys (10-20?) 4. the load of the tranny, 5000 stall convertor, and dana 44 etc. has to account for the rest. That's like 80+ hp loss through the drive train! Is that right? The engine didn't behave like there was something really screwed up on it. Also, I was shocked that a high hp engine would look like a torque motor when viewed through the eyes of a chassis dyno. Thoughts? Anyone else experience something like this?[/quote'] See this all the time at the chassis dyno shop near me . You've joined the club of shocked owners who are comparing their engine dyno numbers to a chassis dyno run. I agree with your driver that the numbers look right to me. A + or - 20 per cent loss with an auto tranny is not uncommon from the engine dyno numbers to the chassis dyno numbers. LARRY Quote Link to comment Share on other sites More sharing options...
Drax240z Posted July 24, 2006 Share Posted July 24, 2006 Typically I'd expect much more than a 20% loss from an auto tranny. Manual trannies are in the 15-20% range typically. Quote Link to comment Share on other sites More sharing options...
Guest Tyler Posted July 24, 2006 Share Posted July 24, 2006 Dang! That's serious loss. Oh well. I guess I'm actually in the ball park then. Cool. Thanks guys. Quote Link to comment Share on other sites More sharing options...
COZY Z COLE Posted July 24, 2006 Share Posted July 24, 2006 Hey TYLER I was in your neck of the woods 2 weeks ago for a family reunion. I had a hell of a time getting to a community center off of I-94. We came up I-35 from Osage,IA and took I-494 in Minneapolis only to find it closed on weekends. The detour was interesting to get to I-94 to say the least. We stayed at a DAYS INN in that area. That part of the country looks like a nice place to live and the pace of living is certainally slower then CA. LARRY Quote Link to comment Share on other sites More sharing options...
titanium Posted July 24, 2006 Share Posted July 24, 2006 Dang! That's serious loss. Oh well. I guess I'm actually in the ball park then. Cool. Thanks guys. Hey Tyler, good to see you joined these forums too! Do you know any of the other Hybrid Z's in MN? I know another one shows up in North Saint Paul every once in a while and I saw a red one with nitrous at CC last year. You should post some pictures up of your car since I didnt get to see it at Car Craft this weekend. Quote Link to comment Share on other sites More sharing options...
Guest xtrmgt Posted July 24, 2006 Share Posted July 24, 2006 I'm in MN but my car is nowhere near drivable yet, actually I haven't even started working on it good to see some more people from MN Quote Link to comment Share on other sites More sharing options...
z-ya Posted July 24, 2006 Share Posted July 24, 2006 Doesn't look like they calibrated the actual engine RPM, with the RPM the dyno is measuring. So this will totally throw off the HP measurements on the chassis dyno. Next time confirm that the chassis dyno RPM matches the RPM on your in car tach. Quote Link to comment Share on other sites More sharing options...
Guest Tyler Posted July 25, 2006 Share Posted July 25, 2006 Hey TYLER I was in your neck of the woods 2 weeks ago for a family reunion. I had a hell of a time getting to a community center off of I-94. We came up I-35 from Osage' date='IA and took I-494 in Minneapolis only to find it closed on weekends. The detour was interesting to get to I-94 to say the least. We stayed at a DAYS INN in that area. That part of the country looks like a nice place to live and the pace of living is certainally slower then CA. LARRY[/quote'] Cool. Feel free to contact me if you are in the area again. It'd be fun to grab lunch or something. You could let me know by posting a message here. I do like living here. I enjoy the season changes. I've not really spent any time in CA out side of long lay overs in a couple of cities. Quote Link to comment Share on other sites More sharing options...
(goldfish) Posted July 25, 2006 Share Posted July 25, 2006 I didn't get time to look at the chassis dyno graph at the show. Could you post it? Admidtly I don't know how the tranny affects the hp/tourqe cross over. Quote Link to comment Share on other sites More sharing options...
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