Cam experts... (Why does the car push through the brakes with a cam in an auto)
06-26-2010, 08:45 AM
#26
Ya, HP Tuners shows the idle at 650 RPM when in gear. It'd odd, sounds like it is at 650 RPM (because it is) but feels like it is at 1500 RPM because of how hard it wants to pull.
I'll play with it some more this week and maybe lower the in gear idle to 600 and see how it reacts. I will also rais it to 950 RPM and see if it makes the problem worse.
I still just don't understand it. At 650 RPM it shouldnt want to pull like it does unless the "pull" that everyone talks about when changing a cam in an automatic is not due to increased idle.
I still just don't understand it. At 650 RPM it shouldnt want to pull like it does unless the "pull" that everyone talks about when changing a cam in an automatic is not due to increased idle.
06-26-2010, 09:05 AM
#27
It is caused by less manifold pressure (vacuum or map pressure) which powers your brakes. Since the brakes aren't functioning like they should this is the reason it surges foward. Raising the idle will help it lowering the idle will make you lose more vacuum thus making the car push even harder through the brakes. Someone correct me if I'm wrong please. Ever wonder why people say oh my car surges at 1400 rpm on the highway. Its because you have a bigger than stock cam that is making the ecu see less map pressure, and when they downshift or get the rpm's up it goes away. Raise your idle to 850 or 950 like you said it should help.
06-26-2010, 09:11 AM
#28
cam without stall is a waste of time I know because I was stupid enough to do it...
my yank3600 is really tight and I have a blast with it in corners on the backroads and hills of Northwest Arkansas, the car is more fun than stock because its so easy to stay in the power band and blast, often without downshifting as deep
cam with stock stall is like flushing $1000-1400 down the toilet, car will be as slow as stock on the strip...getting outrun by bolt on cars while you sit there loping makes you look like a dumbass
my yank3600 is really tight and I have a blast with it in corners on the backroads and hills of Northwest Arkansas, the car is more fun than stock because its so easy to stay in the power band and blast, often without downshifting as deep
cam with stock stall is like flushing $1000-1400 down the toilet, car will be as slow as stock on the strip...getting outrun by bolt on cars while you sit there loping makes you look like a dumbass
06-26-2010, 12:48 PM
#30
It is caused by less manifold pressure (vacuum or map pressure) which powers your brakes. Since the brakes aren't functioning like they should this is the reason it surges foward. Raising the idle will help it lowering the idle will make you lose more vacuum thus making the car push even harder through the brakes. Someone correct me if I'm wrong please. Ever wonder why people say oh my car surges at 1400 rpm on the highway. Its because you have a bigger than stock cam that is making the ecu see less map pressure, and when they downshift or get the rpm's up it goes away. Raise your idle to 850 or 950 like you said it should help.
06-26-2010, 01:16 PM
#32
cam without stall is a waste of time I know because I was stupid enough to do it...
my yank3600 is really tight and I have a blast with it in corners on the backroads and hills of Northwest Arkansas, the car is more fun than stock because its so easy to stay in the power band and blast, often without downshifting as deep
my yank3600 is really tight and I have a blast with it in corners on the backroads and hills of Northwest Arkansas, the car is more fun than stock because its so easy to stay in the power band and blast, often without downshifting as deep
06-26-2010, 01:54 PM
#33
Yeah if your doing 1/4 mile only I would do a 4K or even a 4.5K depending on how high your spinning that bad boy. I am running a 3400 right now funds are low and I am killing myself but she is also my DD and she doesn't lock out till 55mph so city driving sucks 
I think I average 2 gallons per mile in the city 
lol
I think I average 2 gallons per mile in the city lol
06-26-2010, 02:53 PM
#34
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cam without stall is a waste of time I know because I was stupid enough to do it...
my yank3600 is really tight and I have a blast with it in corners on the backroads and hills of Northwest Arkansas, the car is more fun than stock because its so easy to stay in the power band and blast, often without downshifting as deep
cam with stock stall is like flushing $1000-1400 down the toilet, car will be as slow as stock on the strip...getting outrun by bolt on cars while you sit there loping makes you look like a dumbass
my yank3600 is really tight and I have a blast with it in corners on the backroads and hills of Northwest Arkansas, the car is more fun than stock because its so easy to stay in the power band and blast, often without downshifting as deep
cam with stock stall is like flushing $1000-1400 down the toilet, car will be as slow as stock on the strip...getting outrun by bolt on cars while you sit there loping makes you look like a dumbass
06-26-2010, 05:39 PM
#35
This is a dumb statement... Sorry, but it gets old hearing people say **** like this. "Like flushing $1000-$1400 down the toilet. Car will be slow as stock at the strip"???? NO. Lol do not listen to that b.s. You will not loose low end power with a bigger cam unlesss its just purely for high end. And yes you will see gains at the strip with just the bigger cam unless your car isnt running right after. Just on a hot cam install on my lt1, I went from consistant 14.2's to consistang 13.6's with just the hotcam kit for $500. Bigger cam is so much fun on street and also will get good gains on the strip. Not saying a stall will not help ALOT, but you can not say it is like flushing it down the toilet. That is b.s.
Like he said, why would you want a car that runs bolt on times but has a lope shaking the ground? I would rather a stock sounding car that runs cam only times.
I have seen more than one ls1 car with small cams and bolt ons (stock stall) that run simple bolt (or not even that good in some cases) ETs. The MPH is a little better but nothing drastic.
I have seen numerous bolt on cars with converters that run what many cam only setups run.
Not to count a big cam on the street is NOT fun with a stock converter. Hence this thread.
A cam without a converter is a waste if you are looking for ET reduction, period.
It may get old but it is the truth. How many 2010 join date people do you see saying that? How many Vet. tech members do you see saying similar posts to his? There is a reason why we post things similar to what he did, it is the truth. Live and learn I guess.
06-26-2010, 09:16 PM
#36
Okay, all you guys who are posting about the cam not being worth it unless you get a higher stall and those who say do a stall first etc. are not getting the reason for this post. This post has nothing to with that debate which has been discussed in countless threads already.
My question is simple. Why when my car with a 228R-114LSA cam idles in gear at only 650 RPM does it want to push forward so bad at a stop.
The closest I got to an answer was that people thought my brakes may not be up to the task due to the lower vacuum due to the cam but this is not the case. It is not a matter of the brakes not holding the car.. it is a matter of the car wanting to push forward so hard.
So does anyone have any input related to my actual question. Could the stall be locking right at idle or something? One other thing I noticed from the 500 meters I drove the car is it shifts through the gears way to fast. I think it was in 4th gear by the time I was doing 30mph.
My question is simple. Why when my car with a 228R-114LSA cam idles in gear at only 650 RPM does it want to push forward so bad at a stop.
The closest I got to an answer was that people thought my brakes may not be up to the task due to the lower vacuum due to the cam but this is not the case. It is not a matter of the brakes not holding the car.. it is a matter of the car wanting to push forward so hard.
So does anyone have any input related to my actual question. Could the stall be locking right at idle or something? One other thing I noticed from the 500 meters I drove the car is it shifts through the gears way to fast. I think it was in 4th gear by the time I was doing 30mph.
Last edited by NTIMD8; 06-26-2010 at 09:29 PM.
06-26-2010, 09:29 PM
#37
Okay, all you guys who are posting about the cam not being worth it unless you get a higher stall and stall first etc. are not getting the reason for this post. This post has nothing to with that debate which has been discussed in countless threads already.
My question is simple. Why when my car with a 228R-114LSA cam idles in gear at only 650 RPM does it want to push forward so bad at a stop.
The closest I got to an answer was that people thought my brakes may not be up to the task due to the lower vacuum due to the cam but this is not the case. It is not a matter of the brakes not holding the car.. it is a matter of the car wanting to push forward so hard.
So does anyone have any input related to my actual question. Could the stall be locking right at idle or something? One other thing I noticed from the 500 meters I drove the car is it shifts through the gears way to fast. I think it was in 4th gear by the time I was doing 30mph.
My question is simple. Why when my car with a 228R-114LSA cam idles in gear at only 650 RPM does it want to push forward so bad at a stop.
The closest I got to an answer was that people thought my brakes may not be up to the task due to the lower vacuum due to the cam but this is not the case. It is not a matter of the brakes not holding the car.. it is a matter of the car wanting to push forward so hard.
So does anyone have any input related to my actual question. Could the stall be locking right at idle or something? One other thing I noticed from the 500 meters I drove the car is it shifts through the gears way to fast. I think it was in 4th gear by the time I was doing 30mph.
An your stall locking early could also be happening, if you have stock shift points then your stall is going to lock at stock points also, its a simple computer issue, I mean am no tuner but it seems to me that could be the answer.
06-26-2010, 09:40 PM
#38
We have not started the driveability tuning yet.. only idle stuff so far. Oh and he turned off Torque Management.
I dont know if the shifting issue is related to the idle issue at all. I wonder if it shifted so fast due to the fact that it has 4.10 rear gears and the difference in wheel diameter to that of an F-body is throwing everything out of wack. (I.E. the computer/trans doesnt know how fast the car is actually going). This would not explain the reason for why the car wants to push forward so bad. I just thought I would mention this issue since it is also tranny related and there may be some sort of link.
I think I have no choice but to get the project complete to the point where all that is left is the tuning and then trouble shoot each one of my problems one by one.
I'll get a stall which I am sure will solve my issue of pulling at idle but I would still like to know why it is happening. I will spend some more time on this issue and report back if I find anything.
I appreciate the time of all those who tried to help!
-Jason
I dont know if the shifting issue is related to the idle issue at all. I wonder if it shifted so fast due to the fact that it has 4.10 rear gears and the difference in wheel diameter to that of an F-body is throwing everything out of wack. (I.E. the computer/trans doesnt know how fast the car is actually going). This would not explain the reason for why the car wants to push forward so bad. I just thought I would mention this issue since it is also tranny related and there may be some sort of link.
I think I have no choice but to get the project complete to the point where all that is left is the tuning and then trouble shoot each one of my problems one by one.
I'll get a stall which I am sure will solve my issue of pulling at idle but I would still like to know why it is happening. I will spend some more time on this issue and report back if I find anything.
I appreciate the time of all those who tried to help!
-Jason
It could also be a tuning issue I would seriously have your tuner look at it. Those seem to be stock shift points for an A4 if I can remember i think that by 40 or 45 you hit od so if you hit 4th by 30 or 35 your shift points could still be set to stock. But have your tuner look at it and if you tuned it have some one else look at your tune. I am positive after re reading all of us make asses out of our selves that it could be that simple.
06-26-2010, 09:43 PM
#39
I came across this thread which looks to have a lot of great info on tuning the A4. I have not read it all yet but thought I would share the link since some may be interested.
http://www.ls1gto.com/forums/showthread.php?t=356667
http://www.ls1gto.com/forums/showthread.php?t=356667
06-26-2010, 09:46 PM
#40
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