EvilC Posted May 27, 2010 Share Posted May 27, 2010 Ok some background info: Late Sept of 08 car Dyno'd 388whp on a DynoJet. Cam Specs: 228/232 111 .632/.600 Stock LS1 head, LS6 intake, port n polished stock TB. Since then, a ported FAST 90 intake and TB was installed. I also installed a UD pulley. Ok so the car went back to the dyno yesterday, different tuner but also using a DynoJet. The car put down a whopping 370whp and 372whpwith the e cut out open. Very disappointing! I am calling today to get a print out of the afr readings. Before the car went in for the tune, I believe I had a vacuum leak. If I was driving around and came to a complete stop, the rpms would hand up somewhere are 2k. If I then pumped the brakes 3-4 times, the idle would drop to 1k. I thought maybe the check valve on the booster was on backwards but that wasn't the case. So tomorrow I need to spend sometime checking for a leak. Two things come to mind if it makes sense, the vacuum leak would have only been an isssue around idle correct? At WOT doesn't the TB act as a huge "leak"? Wouldn't the vacuum leak be insignificant at that point? Also it was very hot yesterday, 93 out and about 101 in the shop. Tuner states on a cooler day...the number would jump up and 20-30....I dunno guys, only my second time to a dyno so not sure how much that statement holds. Also when the car was strapped down, the driver side wheel was rubbing the body. Enough where a grove was put into the tire...but not a deep. Guess of how much lost there is due to the friction? If all remained the same as in 08, the number drop wouldn't bother me as I know from dyno to dyno end results vary. But with the FAST 90/90 parts installed, a drop of 18whp is a huge deal. Also Joe (Rags) had his car tuned and dyno'd at the same place....he put down 38 more whp than I........guess I can't build a car like Joe!!! We have very similar setups.......input is welcomed guys. Thanks. Quote Link to comment Share on other sites More sharing options...
johnc Posted May 27, 2010 Share Posted May 27, 2010 Ok some background info: Late Sept of 08 car Dyno'd 388whp on a DynoJet. Cam Specs: 228/232 111 .632/.600 Stock LS1 head, LS6 intake, port n polished stock TB. Since then, a ported FAST 90 intake and TB was installed. I also installed a UD pulley. Ok so the car went back to the dyno yesterday, different tuner but also using a DynoJet. The car put down a whopping 370whp and 372whpwith the e cut out open. Very disappointing! I am calling today to get a print out of the afr readings. Before the car went in for the tune, I believe I had a vacuum leak. If I was driving around and came to a complete stop, the rpms would hand up somewhere are 2k. If I then pumped the brakes 3-4 times, the idle would drop to 1k. I thought maybe the check valve on the booster was on backwards but that wasn't the case. So tomorrow I need to spend sometime checking for a leak. Two things come to mind if it makes sense, the vacuum leak would have only been an isssue around idle correct? At WOT doesn't the TB act as a huge "leak"? Wouldn't the vacuum leak be insignificant at that point? Also it was very hot yesterday, 93 out and about 101 in the shop. Tuner states on a cooler day...the number would jump up and 20-30....I dunno guys, only my second time to a dyno so not sure how much that statement holds. Also when the car was strapped down, the driver side wheel was rubbing the body. Enough where a grove was put into the tire...but not a deep. Guess of how much lost there is due to the friction? If all remained the same as in 08, the number drop wouldn't bother me as I know from dyno to dyno end results vary. But with the FAST 90/90 parts installed, a drop of 18whp is a huge deal. Also Joe (Rags) had his car tuned and dyno'd at the same place....he put down 38 more whp than I........guess I can't build a car like Joe!!! We have very similar setups.......input is welcomed guys. Thanks. Meaningless comparison. Its been 18 months and a different shop/dyno. You can't compare the two dyno runs. Right now you've set a new baseline and you must tune from there. Quote Link to comment Share on other sites More sharing options...
blueshark123 Posted May 27, 2010 Share Posted May 27, 2010 Meaningless comparison. Its been 18 months and a different shop/dyno. You can't compare the two dyno runs. Right now you've set a new baseline and you must tune from there. Agreed... I thought when you had told me you said it was the same dyno. Dynojet to Dynojet can vary as different tuners use different correction factors. If it bothers you that much throw the stock intake and tb back on and do a few pulls. If you dont have one you can borrow mine. Also, Joe has ported 5.3L heads that raise compression so you can't compare them to your stock 241 heads. Quote Link to comment Share on other sites More sharing options...
EvilC Posted May 27, 2010 Author Share Posted May 27, 2010 Well small update here, I am 90% sure I have found that the intake manni is leaking at the back where the oil pressure unit. Even with the fact Joe has the 5.3 head the compression bump is not the 40whp difference here. Plus that power was made with a crush bent 2.5 inch exhaust with two 18 inch resinators. I am sure swapping our two exhaust systems won;t give him another 25whp. John, you are right. The only factor that doesn't make sense to me knowing what I think I know....unless one dyno is "playing" with the numbers that should be within 5-7% of one another. That would have been fine with me if the car remained the same but that isn't true. With that said, I know different tuners, different dyno itself not brand. I will just have to drive the car hard and see how it "feels". The bad part is, I swapped this motor from the 73 car over 16 months ago.....everything feels differnt. Funny part is to hear one shop question the tune of another......natural I suppose. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted May 27, 2010 Share Posted May 27, 2010 It's OK Clive, I question you all the time! Apples to oranges.  Rubbing tire, hot weather, different dyno, different capo at the helm, different exhaust and intake.  Throw my G-tech in the car and see what that says. Quote Link to comment Share on other sites More sharing options...
rags Posted May 28, 2010 Share Posted May 28, 2010 I also don't put too much into the numbers. What I am concerned with is the way the idle doesn't come back down after stabbing the throttle as quickly as I think it should, the missing screw that holds the top half of the intake manifold to the bottom half, and the turbulence in the air that can be felt when you put your hand behind the manifold down by the oil pressure sensor. Could be nothing but it doesn't cost anything to pull the manifold and check to make sure something isn't leaking. We'll find out tomorrow. Joe Quote Link to comment Share on other sites More sharing options...
EvilC Posted May 28, 2010 Author Share Posted May 28, 2010 Guys, do understand I am not hung up on the numbers but trying to make sense of the parts added to my motor. Given the negatives right now, I expected similar numbers with the "add ons". I am looking at it like this, you build a NA L28 it makes x amount of power.....you take it to someone else, it should dyno within a certain % range of the first amount. If you dyno a car today at and tomorrow you dyno it somewhere else and it makes 100 less hp...there has to be more to it than just saying, different dyno - different tuner. When a certain combo is known to be in a certain hp range and you are not it raises questions. If I stated my stock LS1 dyno'd 410whp...I hope someone would question that =) Either way, tomorrow I will pull the intake and see what is going on. Trial and error. That is it really. Like John said, I have a different baseline to work from and moving on from there the motor is not where it should be. Quote Link to comment Share on other sites More sharing options...
rags Posted May 28, 2010 Share Posted May 28, 2010 We also have to bring the brake down from upstairs and cut up some sheetmetal to build an airbox to grab some cooler air out in front of the radiator. For both cars. Quote Link to comment Share on other sites More sharing options...
EvilC Posted May 28, 2010 Author Share Posted May 28, 2010 Very tru! Nothing but hot air for my intake right now. Hey it wouldn't be any fun if they always worked the way you wanted them to. Quote Link to comment Share on other sites More sharing options...
jasper Posted May 28, 2010 Share Posted May 28, 2010 (edited) If you suspect a vacuum leak..... They are much easier to find when the engine is running, as opposed to being disassembled. Have you tried the propane, or carb cleaner tricks??? I'm curious about the "feeling turbulence" comment. Are you feeling air movement?? If so...smoke from a cigarette or similar object shows movement very well. You can also pressurize the intake with shop air(Very low pressure) and look for leaks with a spray bottle of soapy water. Lots of tricks available. Don't overlook a crankcase leak, which essentialy is an internal vacuum leak. Also, disconnect the pcv valve, plug the breather, and check for crankcase vacuum, indicating a leak between the intake and crankcase. Edited May 28, 2010 by jasper Quote Link to comment Share on other sites More sharing options...
frank280zx Posted May 28, 2010 Share Posted May 28, 2010 On an engine that size a 'lil' compression bumb can me a whole lot of HP Quote Link to comment Share on other sites More sharing options...
ColtGT4g63 Posted May 29, 2010 Share Posted May 29, 2010 Don't feel bad. On my LS1 I use to run a Torq V2 cam, LS6 intake, 243 heads, single 3.5" exhaust and ran a 7.0 @ 102 in the 1/8th mile. After that, I swapped on Stage2 5.3 heads from TSP, swapped cam to MS3, Fast 92/92, also swapped Exhaust to a Dual 3" with an Xpipe. Could NOT get better then a 7.0 @ 100mph That was on a good day. Average was 7.1 - 7.2 @ 98. Depressing.... Dynoed 411 with the first set up. Didn't even want to know what it would dyno with all the new stuff. Quote Link to comment Share on other sites More sharing options...
EvilC Posted May 29, 2010 Author Share Posted May 29, 2010 Colt, thanks for the info....I know what you mean! Ok, so the manni fold was leaking. When this intake manni was ported, it looks like the rear nut and bolt wasn't installed and no "gasket" was there. So Tommy the starting fluid showed right away there was a leak. One spary and the rpms raised. So took the manni off the head, inspected for leaks, installed some RTV and reinstalled. I just finished so it was to late to start the car back up. Tomorrow will tell if the idle is better and feel for any other leaks. Productive day and will follow up. Quote Link to comment Share on other sites More sharing options...
ColtGT4g63 Posted May 29, 2010 Share Posted May 29, 2010 No problem, glad to hear that you figured out a problem!! Let us know how it goes after the repair. Quote Link to comment Share on other sites More sharing options...
EvilC Posted June 1, 2010 Author Share Posted June 1, 2010 Well I took the car to the track this weekend, road racing, and she felt good. There is no way in hell with the car on the dyno that the tire rub didn't smoke. In hard cornering the cabin filled with white tire smoke. I won't have "new" numbers for a few weeks.....I have another track day in two weekends. Thought I would keep you guys updated. Quote Link to comment Share on other sites More sharing options...
heavy85 Posted June 1, 2010 Share Posted June 1, 2010 Are you still running mass air sensor? If so wouldn't the leak cause it to run lean as the engine was getting more air than it thought? Cameron Quote Link to comment Share on other sites More sharing options...
janaka Posted June 12, 2010 Share Posted June 12, 2010 i found the fast 90/90 to be a huge seat of the pants mod on my car. dyno showed a modest 14rwhp increase or so gain but huge gains on the road. Quote Link to comment Share on other sites More sharing options...
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