Why do I get pulled down low but not top end? (I have a smaller cam)
03-10-2007, 07:53 AM
#1
Why do I get pulled down low but not top end? (I have a smaller cam) Mods are in sig.
I have raced MS3, G5X3, MS4 cars and they all pull me through 1st and 2nd, then it levels off through 3rd and stays even through fourth. All cars are making nearly 20-40 more horspower than me. I have a stock clutch that is probably slipping, so could that be the reason?
I also have the FTRA and all the other cars are Ram-Air TA's, so I thought about the ram-air effect of the FTRA helping out, but doubt that should make a real difference.
I've just been thinking about this and it kinda stumps me why my smaller cam holds its own up top with these bigger cams, but gets dragged down low.
BTW, all these races were done from 20-30mph roll.
If anybody can think of a possible explanation, please share.
Thanks, James.
I have raced MS3, G5X3, MS4 cars and they all pull me through 1st and 2nd, then it levels off through 3rd and stays even through fourth. All cars are making nearly 20-40 more horspower than me. I have a stock clutch that is probably slipping, so could that be the reason?
I also have the FTRA and all the other cars are Ram-Air TA's, so I thought about the ram-air effect of the FTRA helping out, but doubt that should make a real difference.
I've just been thinking about this and it kinda stumps me why my smaller cam holds its own up top with these bigger cams, but gets dragged down low.
BTW, all these races were done from 20-30mph roll.
If anybody can think of a possible explanation, please share.
Thanks, James.
03-10-2007, 08:34 AM
#2
I'll take a stab ... errr, uh ... guess. Maybe you're racing automatics with big converters and a tighter gear pattern/bigger rearend gear. You have long tube headers that don't scavenge power as well down low and LT's toss your power curve in the higher rpm range. Mine is the excat opposite. I have MAC mid-lengths which scavenge better down low and I'm an auto A4 with SS3600 converter and 3.73 rearend gearing. I still haven't been beat off the line out here on the streets, but, the big cam cars always would edge me out up top ... until I installed a WS9 hood with functional ram air and added a 90/90/90 setup. Now, it's still a monster down low, but, up top, the faster I go, the more I pull on these guys ... one guy in particular. I guess it was choking with my 224/228 cam and the added airflow I assume allowed the motor to flow more in/out.
I guess I will change over to long tube headers this summer ... being an A4, it's too much power down low with my setup on the street, which is what I built the car for. Of course, at a well-prep'd track, my guess is that it would give me a better E/T time with a nice 60' time ... hard to say. It's a trade-off of the two and also driver skill at this point. Just my inexperienced .02 worth.
Also looks like you're racing lighter FWD cars, as well ... well maybe some of them are lighter.
I guess I will change over to long tube headers this summer ... being an A4, it's too much power down low with my setup on the street, which is what I built the car for. Of course, at a well-prep'd track, my guess is that it would give me a better E/T time with a nice 60' time ... hard to say. It's a trade-off of the two and also driver skill at this point. Just my inexperienced .02 worth.
Also looks like you're racing lighter FWD cars, as well ... well maybe some of them are lighter.
03-10-2007, 08:43 AM
#3
... couple extra after-thoughts/questions:
... tire compound on your rear corners?
... supension mods?
... any weight reductions on your car?
... have a timeslip ... if so what are you 60'|100'|1/8|1/4 times and top speed?
BTW, to me your dyno looks pretty solid ... through the rpm range, so, looks like you rbigggest enemy might me you lack of traction ... not the low-end power of your car ... just the ability to apply it to the ground at launch.
... tire compound on your rear corners?
... supension mods?
... any weight reductions on your car?
... have a timeslip ... if so what are you 60'|100'|1/8|1/4 times and top speed?
BTW, to me your dyno looks pretty solid ... through the rpm range, so, looks like you rbigggest enemy might me you lack of traction ... not the low-end power of your car ... just the ability to apply it to the ground at launch.
03-10-2007, 11:35 AM
#4
Sorry I should have been more specific. The cars are all 6-speeds also and have the same supporting mods as me but have bigger cams. They have underdrive pulleys and the one with the G5x3 has a FAST 90/90 setup. Traction is somewhat of an issue, but the other cars run street tires also. Would a slipping clutch be more of a problem during first and second where torque multiplication is highest, then not slip as much in 3rd and 4th?
These races are from a 20-30mph roll so its not really a launch issue.
I have no weight reduction other than no spare tire and no front sway bar.
These races are from a 20-30mph roll so its not really a launch issue.
I have no weight reduction other than no spare tire and no front sway bar.
03-10-2007, 12:09 PM
#5
Well i used to wonder about races like this not only f-body vs f-body but other cars that i have seen race for example 03 Cobras vs. f-bodys. Its not your cam that makes your car faster then another car. There are so many other factors that play in when your racing another car especially on the street. For example you have mentioned some of them, traction issues, clutch slippage, weight, different supporting mods, and many others. But i have noticed that weight does play a big role. Well i hope this helps answer your question. I am sure others will chime in.
03-10-2007, 12:52 PM
#6
I understand what you are saying. All cars had the same rear-end gears also. I also raced an 03 cobra that dynoed 478rwhp and 505rwtq from a 20 punch and he pulled me through 2nd and midway through 3rd, then it leveled off and I actually was inching back to his bumper in 4th. He beat me by about 1 to 1 1/2 cars through fourth.
I could see if I was getting pulled through all the gears, since they are putting down alot more hp and I wouldn't think weight difference at higher speeds would matter since your momentum is so high. It just seems to me that I should pull through the lower gears, if anything, then be pulled slowly through the rest of the race.
I guess I'll have to see if a new clutch makes any difference, when I get it.
If anybody else has any insight, please let me know.
I could see if I was getting pulled through all the gears, since they are putting down alot more hp and I wouldn't think weight difference at higher speeds would matter since your momentum is so high. It just seems to me that I should pull through the lower gears, if anything, then be pulled slowly through the rest of the race.
I guess I'll have to see if a new clutch makes any difference, when I get it.
If anybody else has any insight, please let me know.
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03-10-2007, 03:52 PM
#9
Even if you have the same gears .... how tall are your tires/wheels compared to the others? What size rearend gears are you running?
Maybe your weight distribution is lacking compared to theirs ... as was already said, too many factors involved. Good luck pin-pointing the problem ... good you have it nice up top, though.
Maybe your weight distribution is lacking compared to theirs ... as was already said, too many factors involved. Good luck pin-pointing the problem ... good you have it nice up top, though.
03-10-2007, 04:10 PM
#10
These are not just random people that I am racing. They are friends and I know they're mods. The MS4 car has 17x9 stock wheels with street tires. I have 17x9 stock wheels with street tires. All cars have stock 3:42's. The only difference between our cars is the cam.
03-11-2007, 09:01 AM
#12
Originally Posted by mcamarols1
driver mod, maybe
I was hoping I could get some type of technical or physics related explanation.
I'm not so much concerned with losing down low as I am about being about to level out up top. The bigger cams should just keep pulling, atleast that is how I see it. I'm not trying to figure out whats wrong with my car down low, just trying to figure out why the bigger cams don't just keep pulling away.
03-11-2007, 02:45 PM
#13
You know about all your buddies mods, so, I guess that leaves baiscally two things ... tires or the driver ... or both. Your small cam vs their bigger cam is not going to give them the advantage down low and you the advantage up top. That would be backward thinking to believe it's a cam only issue.
Didn't have to think too hard to see that mcamarols1 must have been indicatiing the driver might be the problem. In all sincerity, everyone has already indicated you have a traction problem, and need tires, so, that only leaves the driver launching. You already indicated the clutch slips, which is a no-brainer.
Have you tried driving your buddies cars and have them drive yours to see if the low/top end conditions change when you race?
Didn't have to think too hard to see that mcamarols1 must have been indicatiing the driver might be the problem. In all sincerity, everyone has already indicated you have a traction problem, and need tires, so, that only leaves the driver launching. You already indicated the clutch slips, which is a no-brainer.
Have you tried driving your buddies cars and have them drive yours to see if the low/top end conditions change when you race?
03-11-2007, 04:18 PM
#14
Originally Posted by JEB99TA
Your small cam vs their bigger cam is not going to give them the advantage down low and you the advantage up top.
Even if I suck as a driver, or my clutch has a problem, or my tires....why is it that the bigger cams don't just keep pulling away? This is what I am wondering. Maybe this is a lost cause, but I thought someone might have a technical explanation, or has no one else had races like this?
03-11-2007, 06:32 PM
#15
Originally Posted by Dr. Jeckel
I understand what you are saying. All cars had the same rear-end gears also. I also raced an 03 cobra that dynoed 478rwhp and 505rwtq from a 20 punch and he pulled me through 2nd and midway through 3rd, then it leveled off and I actually was inching back to his bumper in 4th. He beat me by about 1 to 1 1/2 cars through fourth.
I could see if I was getting pulled through all the gears, since they are putting down alot more hp and I wouldn't think weight difference at higher speeds would matter since your momentum is so high. It just seems to me that I should pull through the lower gears, if anything, then be pulled slowly through the rest of the race.
I guess I'll have to see if a new clutch makes any difference, when I get it.
If anybody else has any insight, please let me know.
I could see if I was getting pulled through all the gears, since they are putting down alot more hp and I wouldn't think weight difference at higher speeds would matter since your momentum is so high. It just seems to me that I should pull through the lower gears, if anything, then be pulled slowly through the rest of the race.
I guess I'll have to see if a new clutch makes any difference, when I get it.
If anybody else has any insight, please let me know.
03-11-2007, 10:47 PM
#16
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It could also be this.. Is your cam on a 114, 113, 112, 111? The higher the LSA the more power loss down low, but the more power gained up high.
I raced my friends 122 MPH car today, but he was off spray so its about a 114-115 MPH car off spray.
We went from a 35 MPH punch. All 2nd-3rd we were dead even, and as we hit the tip end of third and shifted into 4th I started walking him. I have the Same cam as you and mines on a 114. I notice that my power range is in 3-4th gear, even with 4:10's.
His car has-Fast90/90. LS6 ported's, LT's, 4:10's, exhaust, clutch and a few little supporting mods. + 150 shot, but he wasnt spraying when we raced.
My mods are in sig.
I raced my friends 122 MPH car today, but he was off spray so its about a 114-115 MPH car off spray.
We went from a 35 MPH punch. All 2nd-3rd we were dead even, and as we hit the tip end of third and shifted into 4th I started walking him. I have the Same cam as you and mines on a 114. I notice that my power range is in 3-4th gear, even with 4:10's.
His car has-Fast90/90. LS6 ported's, LT's, 4:10's, exhaust, clutch and a few little supporting mods. + 150 shot, but he wasnt spraying when we raced.
My mods are in sig.
03-13-2007, 12:32 AM
#19
Originally Posted by Dr. Jeckel
My car weighed 3380.
Car with G5x3, FAST90/90 weighed 3420.
Car with MS3 weighed 3440.
Car with G5x3, FAST90/90 weighed 3420.
Car with MS3 weighed 3440.
03-13-2007, 07:04 PM
#20
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Bigger cams are not always better, especially for a street car with street heads with good low lift flow numbers. Also some grinds have more brute torque and midrange while others are tuned for peak power. All components must be matched to work together. Brute midrange power will win every time on the street if the rest of the variables are held constant including gear ratio. Especially higher gears like 3.42s. The big cam guys with the same stock heads have done nothing but shift their power curve up higher with a little better peak power and sacrifice power down low. At the higher speeds, when you would think the big cam guys would pull away, they are still just getting the motor into the power band.
Two top end packeges on same shortblock:
350 + .060
Flat tops
Bowtie 2.02 heads
.030/.030 Cam 254 @ .050 .485 lift 114 lsa (solid lifter)
12.82 at 107 Shifting at 7000 rpm
350 + .060
Flat tops
1.94 Camel Humps (not ported)
hydraulic flat tappet 230/230 .480/.480 109lsa
12.82 at 107 Shifting at 6000 rpm
Why isn't the bigger cam faster? They are different grinds for different purposes. Also it's plain to see the later is a far better design for a street car and has a way more aggressive profile.
.030/.030 is a "road race" cam from the dark ages. 230/230 .480/.480 is a street cam from a little more recent times. Realistically, the old vette cam is more like a 236 dur hydraulic with .455 lift net of the lash with a lazey torqueless profile.
As for the slipping clutch, on a street car from a rolling start, that kills you on shifts durring release. The clutch spins when you should be accelorating. If you both have the same non grippey street tires, you spin while the big cam guys pull you at low speeds and you with the strong mid range motor start to catch them at the higher speeds in the midrange rpm.
There really are too many possible variables including the possibility that you spin at the beginning and your talanted driving is catching them when they shift...
Driving is the biggest variable of all. I remember spanking a new f-body on the street 4 years back with a stock 327 from an impala and the lazey 350 hp 327 vette hydraulic cam and we both had manual transmissions. It was obvious I killed him at every shift. His car should have been faster and I know it had more power. Everytime he shifted I pulled away further. I left the gas on the floor the entire time. He did not.
Have fun!
Two top end packeges on same shortblock:
350 + .060
Flat tops
Bowtie 2.02 heads
.030/.030 Cam 254 @ .050 .485 lift 114 lsa (solid lifter)
12.82 at 107 Shifting at 7000 rpm
350 + .060
Flat tops
1.94 Camel Humps (not ported)
hydraulic flat tappet 230/230 .480/.480 109lsa
12.82 at 107 Shifting at 6000 rpm
Why isn't the bigger cam faster? They are different grinds for different purposes. Also it's plain to see the later is a far better design for a street car and has a way more aggressive profile.
.030/.030 is a "road race" cam from the dark ages. 230/230 .480/.480 is a street cam from a little more recent times. Realistically, the old vette cam is more like a 236 dur hydraulic with .455 lift net of the lash with a lazey torqueless profile.
As for the slipping clutch, on a street car from a rolling start, that kills you on shifts durring release. The clutch spins when you should be accelorating. If you both have the same non grippey street tires, you spin while the big cam guys pull you at low speeds and you with the strong mid range motor start to catch them at the higher speeds in the midrange rpm.
There really are too many possible variables including the possibility that you spin at the beginning and your talanted driving is catching them when they shift...
Driving is the biggest variable of all. I remember spanking a new f-body on the street 4 years back with a stock 327 from an impala and the lazey 350 hp 327 vette hydraulic cam and we both had manual transmissions. It was obvious I killed him at every shift. His car should have been faster and I know it had more power. Everytime he shifted I pulled away further. I left the gas on the floor the entire time. He did not.
Have fun!
Last edited by Vintage Iron55; 03-13-2007 at 07:10 PM.