Keith Posted March 18, 2005 Share Posted March 18, 2005 I am going to get my Dyno certification tomorrow and had a look at the Dyno Cert. Sheet. I want to make sure I understand what is being asked... Ignition Timing - I have the stock, unmolested LT1 ignition system. How should I answer this one? Do I really have to have the Dyno tech verify this? Fuel Pressure - I have the stock, unmolested LT1 fuel system (from fuel pump to injectors). Do I really need this verified by the dyno operator? Head pipe size - don't we have to have stock exhaust manifolds or is this asking something else? Also, I don't know if I will be able to get the water temp to 225 degrees. I've never seen it get that hot (I have a HUGE oil cooler).... Quote Link to comment Share on other sites More sharing options...
Keith Posted March 19, 2005 Author Share Posted March 19, 2005 30 hits and no replies? I also assume that the dyno run needs to be in SAE mode, correct? I leave in a few hours. BTW - I weighed my car yesterday. See last 3 pics in sig for weight. Oink! Oink! I'll post scans of my dyno runs later today. Quote Link to comment Share on other sites More sharing options...
Guest Posted March 19, 2005 Share Posted March 19, 2005 Sorry Keith, I have just been through the dyno stuff and this is what I found. Not sure about base timing but fuel pressure should be taken and noted, as far as temparature, they put a cover over my radiator to stop all air flow and warmed it up on the dyno and it got to temparature. You are correct regarding the manifolds, ne need to measure since they are stock. Good l;uck and have fun. Keith Quote Link to comment Share on other sites More sharing options...
Guest Posted March 19, 2005 Share Posted March 19, 2005 It would be nice to have an offical response on this because Keith asks some very good questions. There is about a 5 percent difference between the results of the SAE and STD correction factors. STD results in a higher number and that's what most aftermarket dyno operators typically use. Regarding your other questions, I think the head pipe diameter refers to the size of the X- or H-pipe tubing connected to your stock exhaust manifolds, and you should be able to verify the initial and total ignition timing of your engine. Even on an LT1, since the base timing can be changed it should be recorded during the test. I bet you'll have no problem getting the water temp up to 225 once you go to wide-open throttle at full load a few times with basically no air flow though the radiator. I'm not wild about running my engine that hot either, but hopefully it will be the only time you have to do it depending on how good your radiator and cooling system are. Quote Link to comment Share on other sites More sharing options...
King Matt1548534716 Posted March 19, 2005 Share Posted March 19, 2005 Sorry, that was me above. I though we were going to change the log-in thing. Quote Link to comment Share on other sites More sharing options...
Keith Posted March 19, 2005 Author Share Posted March 19, 2005 Thanks for the information, Matt. The thought of running it that hot terrifies me. It's the original, stock, unopened motor - with 109,000 miles on it and I am the 3rd owner to road race it. I suppose if it has to be then it has to be. I asked about SAE mode because there was an AI post at nasaforums over the winter stating that this is the mode that the dyno needed to be run in for AI tests. I just assumed that this would be the same for CMC... I guess if I run in SAE and it was supposed to be STD then I can get re-checked at Mid Ohio. Yeah, I understand that the timing can be changed but it seems kinda pointless to check it during this test. If I had a mind to cheat, I would reduce power for the test then put it back later. The reality is that it wouldn't work at our events anyway - when you come off the track, you will very likely be weighed and dynoed if you run well so the effort seems pointless... In fact, I don't even know how to change the timing or the fuel pressure on my car... Head pipe size - I bought a used SLP y-pipe and cat and have it on the car. I just checked their website and the piece is no longer list... Hmmm... I'll post the dyno results later today. Quote Link to comment Share on other sites More sharing options...
Members Al F. Posted March 24, 2005 Members Share Posted March 24, 2005 Keith Sorry for the late reply, I've been unbeliveably busy lately. Head pipe refers to the exhaust immediately downstream of the exhaust manifolds. LT1 owners dont need to worry about timing since that gets changed by changing programs (which you're not allwed to do). Fuel pressure however definitely must be recorded, as this can be adjusted and may be teched at the track. Remember, the entire dyno sheet must be filled out and kept with the dyno curves as you may be asked for these at the track at any time. I havent had any problems getting my car to 225. We shut all the floor fans off, and hold it at a high idle. It usually takes about 10 minutes. As soon as the temp hits 225 I drop it in gear, nail it, and a buddy turns on every fans. Quote Link to comment Share on other sites More sharing options...
Richard Pryor1548534703 Posted March 24, 2005 Share Posted March 24, 2005 Al, I think this topic highlights a problem with the dyno results...no self respecting CMC racer would allow his car to run at 225 degrees on the track...most are in the 190 range give or take 5 degrees....and here's the rub....when you average the three dyno runs you are generally, almost always, going to have a significant power dropoff on the 225 run and when you average that in with the other two you are going to get a "low" reading....which real world translates to cars on the track running at their 180 degree run horsepower which is over the 230/300 legal figure....due to the loophole of a nonrealistic 225 dyno run being averaged in you are getting skewed figures....this is especially true with 4th gen F bodies (believe me I know)...my suggestion is for the dyno runs to incorporate and average only the two lower runs or even allow only the highest run for the sake of legality as the racer will always setup his car for maximum power/cooling; all the 225 degree run does is allow extra on the track horsepower for certain cars (some benefit more than others)...just a thought but if this isn't changed expect to see more and more 4th gens walk away from the pack....Richard Quote Link to comment Share on other sites More sharing options...
King Matt1548534716 Posted March 27, 2005 Share Posted March 27, 2005 I actually agree with Richard on this one, because what the water temperature rule doesn't take into account is oil temperature, and not just engine oil. Transmission and differential fluid temps have a big effect on frictional losses in the drivetrain as well. Keith O. just posted the results of his LT1 dyno test and it actually made more power on the higher water temp pulls, most likely because the engine oil and fluid temps in the drivetrain were getting up to operating temperature in the second and third pulls. Quote Link to comment Share on other sites More sharing options...
mitchntx1548534714 Posted March 27, 2005 Share Posted March 27, 2005 Matt, I think you are a little over the top on this. I do not disagree with your comments. They are valid and true. However, dynoing in 100* August heat, the weight of the wheels, etc will have the same if not more affect than fluid temps in the trans and diff. Hell, I've seen a 10% variance between chassis dynos, on the same car under near identical conditions. It's just not that exacting ... Quote Link to comment Share on other sites More sharing options...
King Matt1548534716 Posted March 27, 2005 Share Posted March 27, 2005 Mitch, The reason you see such variation in chassis dyno results is because most dyno operators make very little effort to control the variables like water and oil temperature. It's difficult to do without instrumenting the dyno and the car, but even a Dynojet can produce consistent, repeatable results if it's used properly. Simple things like the tension on the straps holding the tires on the roller can make a difference. If the weight of the wheels and tires is constant, it's not a factor, but there will be a difference in the results on an inertia dyno if you test with light vs. heavy wheels, a lighter driveshaft or flywheel, change gears, or make any change that affects friction or intertia in the drivetrain. If you have seen a laboratory-grade dyno facility in operation, with closed-loop oil and water temp control and a climate-controlled cell, you'll be horrified at how unscientific most aftermarket dynos are. I've done engine dyno testing at Katech for instance where the variation between 3 consecutive runs was less than 0.5 hp. In the real world of CMC racing, we have to live with what we've got, which may be imperfect, but hopefully is consistent for all competitors on any given day. Quote Link to comment Share on other sites More sharing options...
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