Finally got my carb'd LS project on the street
12-01-2011, 01:06 PM
#43
I actually used the F-body accessories. Main reason was because I also own a 4th Gen F-body and thought it would be nice to have the two cars share as many common parts as possible.....just to make it easier to keep spares on hand or rob from one to fix the other in an emergency (alternator failure, etc.)
Where are you at in Western PA? I grew up in NW PA.....Franklin/Oil City area.
01-15-2012, 01:10 PM
#44
I went back to the track yesterday to do some more testing and I have some interesting results to share. My previous best ET/MPH were achieved through a full 3-inch exhaust with an x-pipe, Flowmaster 40-series mufflers, and full tail pipes. So this time out, I wanted to see if there was anything to be gained with by ditching the exhaust system and running open headers. Since I had already set a baseline "best time" with the exhaust on, I took the exhuast off before heading to the track. To achieve a fair standard for comparing runs made on different days, I have corrected all my timeslips down to a DA of 0ft. This should eliminate any day to day weather effects on power.
So just as a reminder, here are the conditions and results of my previous best pass made on 19 November.
Previous Best (through exhaust)
DA: 4572ft
Launch: 3800RPM
60’: 1.70
1/8: 7.49
MPH: 92.73
1/4: 11.74
MPH: 115.41
This pass corrects to 11.07@122.34 at a DA of 0ft
And now for my results from yesterday......
First Pass (without exhaust)
DA: 3908ft
Launch: 3800RPM
60’: 1.67
1/8: 7.33
MPH: 94.36
1/4: 11.50
MPH: 117.63
This pass corrects to 10.95@123.60 at a DA of 0ft
Initially this pass looks to have shown an impressive gain over my previous best. Even when comparing the corrected times, this is .12 sec quicker and 1.25 MPH faster than my previous best. However, the first thing to consider is that the exhaust I removed weighed 71 lbs. Following the rule of thumb that says a 100lb weight reduction is equal to about .1 sec ET reduction initially tells me this gain was mostly from the weight savings. However, based on my next two runs, I'm thinking even more so that this gain was almost completely because of the intake manifold and carburetor being completely cold on the first pass and had nothing to do with the exhaust at all. You'll see why in a second when you look at my second and third passes with no changes made to the car at all besides heat soak.
Second Pass (without exhaust)
DA: 3908ft
Launch: 3800RPM
60’: 1.70
1/8: 7.43
MPH: 94.24
1/4: 11.62
MPH: 116.98
This pass corrects to 11.06@122.92 at a DA of 0ft
The interesting thing about this pass is that it was made in the same DA as the first pass, just 30 mins later. So the only difference between these two passes was the amount of heat the intake had soaked up. The engine was warmed up to around 150 for the first pass, but I'm certain the intake wasn't very warm. The water temp was the same on the second pass, but I'm certain the intake was heat soaked after sitting only 30 minutes. So for this reason I consider my first pass to be a cold "throw away" pass. Now compare the corrected time on my second pass with the corrected time of my "previous best with exhaust" pass. You'll see there was virtually no gain at all in ET and a very modest MPH gain without the exhaust, as the corrected times were almost identical. But wait there's more....... I still wanted to make a third pass to backup to the second heat soaked run. The third pass was made 45 mins later in slightly worse DA.
Third Pass (without exhaust)
DA: 4100ft
Launch: 3800RPM
60’: 1.72
1/8: 7.46
MPH: 93.58
1/4: 11.67
MPH: 116.46
This pass corrects to 11.08@122.96 at a DA of 0ft
Notice how the 60', ET, and MPH all fell off slightly from the second pass due to the slightly higher DA. Yet the corrected ET and MPH again almost exactly match both the second pass and my previous best with exhaust. To me this again proves there was no gain by removing the exhaust.
Next up was to test with the addition of a 1-inch HVH Super Sucker carb spacer. I have heard mixed results with these things so of course I had to try it for myself. All I can say is that I'm "skeptically" pleased with my purchase. The results speak for themself, but with one caveat that I will address in a minute.
Fourth Pass (without exhaust/added HVH spacer)
DA: 4300ft
Launch: 3800RPM
60’: 1.64
1/8: 7.33
MPH: 94.32
1/4: 11.51
MPH: 117.19
This pass corrects to 10.90@123.79 at a DA of 0ft
Man was I happy after this pass! Notice the DA was up an additional 200ft from my last pass, yet I ran my second quickest/fastest pass of the day. Comparing this pass's corrected values to that of my 2nd and 3rd passes, I show an average "corrected" gain of .17 and .85 MPH. My only skeptasim with this gain is that the intake was allowed to cool more, both before and during the install of the spacer. In fact, there was almost 2 hours between pass number three and pass number four. So one might say it is more fair to compare pass four to pass number one when the intake was much cooler. When you make that comparison, you still see a "corrected" gain of .05 sec and .19 MPH with the spacer. But I'm here to tell you that, even with almost two hours to cool, the intake was still much warmer on pass four than it was on pass one. The real test would have been to make one more pass with the spacer after a shorter cool down period, but unfortunately the staging lanes closed before I could make that happen. So I guess that just gives me an excuse for more testing another day.
Given my results this far I have drawn these two conclusions:
1. The exhaust is going back on the car and will probably stay there.
2. The HVH spacer was worthwhile, even if the intake temp is questionable.
So just as a reminder, here are the conditions and results of my previous best pass made on 19 November.
Previous Best (through exhaust)
DA: 4572ft
Launch: 3800RPM
60’: 1.70
1/8: 7.49
MPH: 92.73
1/4: 11.74
MPH: 115.41
This pass corrects to 11.07@122.34 at a DA of 0ft
And now for my results from yesterday......
First Pass (without exhaust)
DA: 3908ft
Launch: 3800RPM
60’: 1.67
1/8: 7.33
MPH: 94.36
1/4: 11.50
MPH: 117.63
This pass corrects to 10.95@123.60 at a DA of 0ft
Initially this pass looks to have shown an impressive gain over my previous best. Even when comparing the corrected times, this is .12 sec quicker and 1.25 MPH faster than my previous best. However, the first thing to consider is that the exhaust I removed weighed 71 lbs. Following the rule of thumb that says a 100lb weight reduction is equal to about .1 sec ET reduction initially tells me this gain was mostly from the weight savings. However, based on my next two runs, I'm thinking even more so that this gain was almost completely because of the intake manifold and carburetor being completely cold on the first pass and had nothing to do with the exhaust at all. You'll see why in a second when you look at my second and third passes with no changes made to the car at all besides heat soak.
Second Pass (without exhaust)
DA: 3908ft
Launch: 3800RPM
60’: 1.70
1/8: 7.43
MPH: 94.24
1/4: 11.62
MPH: 116.98
This pass corrects to 11.06@122.92 at a DA of 0ft
The interesting thing about this pass is that it was made in the same DA as the first pass, just 30 mins later. So the only difference between these two passes was the amount of heat the intake had soaked up. The engine was warmed up to around 150 for the first pass, but I'm certain the intake wasn't very warm. The water temp was the same on the second pass, but I'm certain the intake was heat soaked after sitting only 30 minutes. So for this reason I consider my first pass to be a cold "throw away" pass. Now compare the corrected time on my second pass with the corrected time of my "previous best with exhaust" pass. You'll see there was virtually no gain at all in ET and a very modest MPH gain without the exhaust, as the corrected times were almost identical. But wait there's more....... I still wanted to make a third pass to backup to the second heat soaked run. The third pass was made 45 mins later in slightly worse DA.
Third Pass (without exhaust)
DA: 4100ft
Launch: 3800RPM
60’: 1.72
1/8: 7.46
MPH: 93.58
1/4: 11.67
MPH: 116.46
This pass corrects to 11.08@122.96 at a DA of 0ft
Notice how the 60', ET, and MPH all fell off slightly from the second pass due to the slightly higher DA. Yet the corrected ET and MPH again almost exactly match both the second pass and my previous best with exhaust. To me this again proves there was no gain by removing the exhaust.
Next up was to test with the addition of a 1-inch HVH Super Sucker carb spacer. I have heard mixed results with these things so of course I had to try it for myself. All I can say is that I'm "skeptically" pleased with my purchase. The results speak for themself, but with one caveat that I will address in a minute.
Fourth Pass (without exhaust/added HVH spacer)
DA: 4300ft
Launch: 3800RPM
60’: 1.64
1/8: 7.33
MPH: 94.32
1/4: 11.51
MPH: 117.19
This pass corrects to 10.90@123.79 at a DA of 0ft
Man was I happy after this pass! Notice the DA was up an additional 200ft from my last pass, yet I ran my second quickest/fastest pass of the day. Comparing this pass's corrected values to that of my 2nd and 3rd passes, I show an average "corrected" gain of .17 and .85 MPH. My only skeptasim with this gain is that the intake was allowed to cool more, both before and during the install of the spacer. In fact, there was almost 2 hours between pass number three and pass number four. So one might say it is more fair to compare pass four to pass number one when the intake was much cooler. When you make that comparison, you still see a "corrected" gain of .05 sec and .19 MPH with the spacer. But I'm here to tell you that, even with almost two hours to cool, the intake was still much warmer on pass four than it was on pass one. The real test would have been to make one more pass with the spacer after a shorter cool down period, but unfortunately the staging lanes closed before I could make that happen. So I guess that just gives me an excuse for more testing another day.
Given my results this far I have drawn these two conclusions:
1. The exhaust is going back on the car and will probably stay there.
2. The HVH spacer was worthwhile, even if the intake temp is questionable.
Last edited by GC99TA; 01-15-2012 at 01:17 PM.
01-15-2012, 02:03 PM
#47
Launching!
Join Date: Jun 2011
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That's a rocking street car!
Bruce
01-15-2012, 02:07 PM
#48
Gotcha, and thanks again! I just didn't want anyone to think I was trying to say the car did something that it didn't do.....LOL. Hopefully when I get back east late this summer, I can take the car to MIR (80ft actual elevation) and make some passes on a cool fall evening and get an actual 10 second slip!
01-15-2012, 02:55 PM
#49
Nice results. Were you using 87 Octane gas this time as well?
I have many acquaintances that have gone faster once they changed out their restrictive Flowmaster mufflers for something straight through like a Dynomax UltraFlo.
I have many acquaintances that have gone faster once they changed out their restrictive Flowmaster mufflers for something straight through like a Dynomax UltraFlo.
01-15-2012, 03:12 PM
#50
Nice results. Were you using 87 Octane gas this time as well?
I have many acquaintances that have gone faster once they changed out their restrictive Flowmaster mufflers for something straight through like a Dynomax UltraFlo.
I have many acquaintances that have gone faster once they changed out their restrictive Flowmaster mufflers for something straight through like a Dynomax UltraFlo.
I'm curious now if changing out the mufflers for something less restrictive than the Flowmasters would even matter at this point? Seeing as how the car ran basically the same with and without exhaust, it seems the Flowmasters aren't really causing a restriction at my current power level? Of course, once I make more power in better air conditions (closer to sea level), all this testing may be out the window? I'm sure the 87 will be out the window at that point too......
Maybe once I get to a point where the current exhaust slows the car down, I'll try something straight through like the Dynomax's. I'll have to search for some similar combo's running them to see how they sound. Thanks for the suggestion.
01-15-2012, 09:43 PM
#52
Thanks man. The car actually already has a chromoly 10-point cage so I'm still in overkill mode . Yeah.......I anticipated early on that this car would get out of hand so I over built mostly everything.......except the rear end....... . That will be my next major expense.
. Yeah.......I anticipated early on that this car would get out of hand so I over built mostly everything.......except the rear end....... . That will be my next major expense. 
01-16-2012, 07:39 AM
#54
Launching!
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I'm curious now if changing out the mufflers for something less restrictive than the Flowmasters would even matter at this point? Seeing as how the car ran basically the same with and without exhaust, it seems the Flowmasters aren't really causing a restriction at my current power level?
How much flow do your Flowmasters have? You can use the dynomax chart http://www.dynomax.com/assets/2010ca...ch_section.pdf to determine what the current flow will. I noticed a 40 series flowmaster in the dynomax vt advertisment are showing about 372 CFM but its only 2.5" so if you take into account 3' you are still goign to flow about 1.44 X that.... so about 536 CFM and knowing marketing Dynomax picked a lower flowing model... even at this you have about 490-500 loose free Hp according to the flow table in the Dynomax tech section.
So will you gain much? I don't think so. You might gain some however. How much more than 500 are you making? Then take a small percentage of that difference. Also have to take account for area under the curve. Having a slight restriction may help low to mid range power some. Also your loss is only most likely at the very top of your RPM band.
For my car I might take the risk on the Dynomax VT but the spring scares me in terms of how long will they last? I want to keep my car a quiet as possible when driving around town as the Police can be nasty here ............ But at WOT they should not affect power any and supposedly get rid of the drone.... and I live about 45 Miles to work and would like to drive my car to work and the drone could get annoying after a bit.
Bruce
01-16-2012, 01:05 PM
#55
Thanks man...I'm having a blast with it so far!
Thats an interesting chart.....thanks for the link. I'm guessing whatever amount of restriction (or lack thereof) is in my current system is optimized for my current combo since I neither gained nor lost with/without the exhaust. Im not sure how much more than 500 I'm making at the flywheel, but I'm guessing not much, if any at all, at this elevation. Of course all of this could change at sea level; the exhaust system could become a slight restriction if the car made significantly more power down there......but still probably not a crippling restriction I guess.
Those VT's are an interesting concept, but I think I'd have the same apprehension as you with the internal springs. Does your current system have an x-pipe? I can't swear to it, but I credit my x-pipe with the lack of drone in my system. I get no drone or rasp at all with my system at any RPM I cruise at, but I've ridden in other cars (with H-pipes or no crossover) where it was unbearable. You definately don't want to be miserable driving your car or you never will drive it at all......at least that's how I am.
Changing to dynomax, might give you a small amount but not sure how much?
How much flow do your Flowmasters have? You can use the dynomax chart http://www.dynomax.com/assets/2010ca...ch_section.pdf to determine what the current flow will. I noticed a 40 series flowmaster in the dynomax vt advertisment are showing about 372 CFM but its only 2.5" so if you take into account 3' you are still goign to flow about 1.44 X that.... so about 536 CFM and knowing marketing Dynomax picked a lower flowing model... even at this you have about 490-500 loose free Hp according to the flow table in the Dynomax tech section.
So will you gain much? I don't think so. You might gain some however. How much more than 500 are you making? Then take a small percentage of that difference. Also have to take account for area under the curve. Having a slight restriction may help low to mid range power some. Also your loss is only most likely at the very top of your RPM band.
For my car I might take the risk on the Dynomax VT but the spring scares me in terms of how long will they last? I want to keep my car a quiet as possible when driving around town as the Police can be nasty here ............ But at WOT they should not affect power any and supposedly get rid of the drone.... and I live about 45 Miles to work and would like to drive my car to work and the drone could get annoying after a bit.
Bruce
How much flow do your Flowmasters have? You can use the dynomax chart http://www.dynomax.com/assets/2010ca...ch_section.pdf to determine what the current flow will. I noticed a 40 series flowmaster in the dynomax vt advertisment are showing about 372 CFM but its only 2.5" so if you take into account 3' you are still goign to flow about 1.44 X that.... so about 536 CFM and knowing marketing Dynomax picked a lower flowing model... even at this you have about 490-500 loose free Hp according to the flow table in the Dynomax tech section.
So will you gain much? I don't think so. You might gain some however. How much more than 500 are you making? Then take a small percentage of that difference. Also have to take account for area under the curve. Having a slight restriction may help low to mid range power some. Also your loss is only most likely at the very top of your RPM band.
For my car I might take the risk on the Dynomax VT but the spring scares me in terms of how long will they last? I want to keep my car a quiet as possible when driving around town as the Police can be nasty here ............ But at WOT they should not affect power any and supposedly get rid of the drone.... and I live about 45 Miles to work and would like to drive my car to work and the drone could get annoying after a bit.
Bruce
Those VT's are an interesting concept, but I think I'd have the same apprehension as you with the internal springs. Does your current system have an x-pipe? I can't swear to it, but I credit my x-pipe with the lack of drone in my system. I get no drone or rasp at all with my system at any RPM I cruise at, but I've ridden in other cars (with H-pipes or no crossover) where it was unbearable. You definately don't want to be miserable driving your car or you never will drive it at all......at least that's how I am.
01-16-2012, 02:22 PM
#56
Launching!
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Does your current system have an x-pipe? I can't swear to it, but I credit my x-pipe with the lack of drone in my system. I get no drone or rasp at all with my system at any RPM I cruise at, but I've ridden in other cars (with H-pipes or no crossover) where it was unbearable. You definately don't want to be miserable driving your car or you never will drive it at all......at least that's how I am.
Bruce
01-17-2012, 08:00 PM
#57
On The Tree
Sometimes you need to add jetting when you reduce the backpressure. Every car is different. Also as the air inlet temp goes up the airflow goes down just because hot air takes up more space. Maybe the jetting needs to be adjusted.
Aleck
Aleck
01-17-2012, 09:02 PM
#58
01-17-2012, 09:17 PM
#60
I was thinking the same thing. I had it idling leaner at one point, but it was so lean that it would shut down if I jumped on the throttle and then let off quickly (like after a quick burnout). So I slowly fattened it up until it quit doing that. But of course that was in much different weather than now, so I probably need to give it another try.
I do have a wideband but it's on my Trans Am, which is in storage in Pennsylvania.....LOL. But I may get another one for this car since the one in the TA is more of a "pemanent" install (aka, pain in the *** to take back out for temporary use). I have a couple bungs that I'm probably going to weld into my exhaust before I put it back on. I know I really only need one bung, but my buddy has a FAST wideband with dual sensors that I may be able to borrow at some point.
I do have a wideband but it's on my Trans Am, which is in storage in Pennsylvania.....LOL. But I may get another one for this car since the one in the TA is more of a "pemanent" install (aka, pain in the *** to take back out for temporary use). I have a couple bungs that I'm probably going to weld into my exhaust before I put it back on. I know I really only need one bung, but my buddy has a FAST wideband with dual sensors that I may be able to borrow at some point.