guys w/ cams come on it

[steveb24]

just wondering if u guys with cams experience some harsh 1500 rpm and below bucking, tossing, and crunching of the drivetrain. its pretty annoying and i wana know how to help decrease its effect. i mean, i cant even brake properly cause i gotta push the clutch in so early. what are you guys' thoughts and what do u do?

 

[hotmustang331]

Same problem here...anthing below 1500RPMs would cuase the car to start bucking. 2nd and 3rd gear would get HARSH. I just drove around it, and after a while I was able to completely avoid it without giving it much thought. I just push the clutch in @ around 1500RPM in 5th and really never down shifted as I slowed down...just kept it in neutral usually. Or rowed down through the gears with the clutch in.

In my case it would really only get "bad" if I let it get down to 1000-1200RPMs in 2nd-3rd with no throttle applied. Push on the gas and it would basically go away. Im not sure how this can be fixed...has to be a tuning issue of some sort.

 

[steveb24]

yup.. same cams, same EXACT thing.. its soo annoying

 

[jasonh_86]

I've got that problem. It was worse the last time my cams were installed. But now that they're properly installed and degreed it's not quite as bad. It'll do it on occasion, but I usually have to make it do it... but yeah, its pretty annoying.

 

[stangman]

never had that problem

fwiw... i had tim, at MPH, tune my car

 

[hotmustang331]

^Me too . So not sure what the problem is....im sure Tim could resolve it for us though.

 

[TGJ]

It seems that the cars that are doing this have VT Stg 1 cams. I am not sure that it is not linked to the tighter LSA that the VT cams have. I don't have this issue with my car and I am running a larger cam( Crower PI Stg 2 SC cam ) than that.

 

[hotmustang331]

Could be...but the STG 2 cams have an even tight LSA of 108 I believe. STG 1 is 110 if im not mistaken. Maybe us stg 1 guys are in that "sweet spot" where that would happen.

 

[96BlueStangGT]

My Comp 268's do it on occasion.

 

[rrl]

mine does it also so i just downshift more or else when i'm slowing down i put it in neutral.i also have vt stage1.

 

[LaserRed01GT]

You are not supposed to be using the engine to brake anyway, that's why we have a brake pedal (the one in the middle). You are cutting your clutch life in half by downshifting through the gears to brake the car.

The PCM using a different set of scalars/tables upon throttle close and decel. Tuners will not mess with the fuel cutoff decel constants to accomdate for a different cam becuase they don't expect people to be trying to engine brake at every stop light.

 

[SaleenGT2001]

i always use the engine to slow down. i dont have cams (yet) so i obviously dont have the problem

 

[steveb24]

You are not supposed to be using the engine to brake anyway, that's why we have a brake pedal (the one in the middle). You are cutting your clutch life in half by downshifting through the gears to brake the car.

The PCM using a different set of scalars/tables upon throttle close and decel. Tuners will not mess with the fuel cutoff decel constants to accomdate for a different cam becuase they don't expect people to be trying to engine brake at every stop light.

yeah yea yea.. but its still annoying and didnt do it when stock. not even thinkin about removing the cams or anything, since they made a nice gain.. but if i had a blower than they would be gone.

 

[Fast Eddie 41]

Easy fix.....quit using your engine compression to slow the car down. We have 4 disc brakes...use them.

 

[steveb24]

i dont think you guys are getting it. whether i use my brakes or not it still does the same exact thing. and when u use your brakes is starts faster than u expect it too and really violently shakes the drivetrain and entire car around. so its NOT the brakes.. its pretty obvious that its caused by the way the cams shake the motor when not under throttle, which in turn shakes the drivetrain. i was just lookin for some input form other frustrated people. now enough about damn brakes.

 

[hotmustang331]

Engine breaking is a more efficient way of slowing down. If your in 4th, leave it there until you get to near idle. It assits in your breaking and it doesnt hurt anything.
We arnt going from 5th to 4th to 3rd to 2nd and letting it shake each time. AOur problem comes from when we are in traffic usually and are staying in lower gears...starting and stopping. You really cant idle in 1st gear if the traffic is moving slowly, thats more or less where we are having issues.

But like I said, im not ANYWHERE near the point of wanting to take the cams out....even when the turbos are fully done, they are staying in. I love the sound and added performance too much...its not hard for me to push the clutch in @ 1500RPMs and im not in traffic often.

 

[Matt's 03 GT]

Just put the car in Neutral when decelerating.

 

[steveb24]

i like the advice and all but you really wouldnt understand unless you drive it everyday all over town. yeah i do know putting it in neutral stops the shaking but u just cant always do that when u need to be on and off.. anyways, i did a little testing this afternoon by taking back 2 degrees of timing in our shaking range (0-2000 rpm) and it seemed to help a bit. now that leaves me at 12* for that range and 16* for the others. does that cause any problems having that wide of a gap? if not imma bring it down to 10* and see what happens.

 

[Fast Eddie 41]

If you guys are having this much of a problem with idle and cam surge with little Stage 1 and 2 cams....I hate to say it.... but your tune is way off then. We have tuned 4.6 2 valve cars with much...much bigger cams than these popular "Stage 1&2" grinds and idled perfect and had minimal surge.

Did you guys get these dyno tuned under a load?

We've had some guys come in before that had cams and a mail order tune (some tunes from some very well known places that I won't mention) and the spark tables (curves) had been purposely manipulated so that they weren't affected by load. That is unusual, and in my opinion not good. Sure it makes the tune nice and safe but it is not the most "efficient" way of making good power....load tuning in my opinion is the only way. You leave so much HP on the table by separating load influence from spark. These MAF curves (transfer fucntions) were off to. You can get the MAF setup pretty darn close...but it's always wise to get her on a dyno...datalog...and dial in the MAF the right way.

 

[hotmustang331]

^Thats probably Tim @ MPH, he one of a few that doesnt set it up based on load.
Here is what he said,

"I tune totally different than most tune files I've seen from other shops. I set spark curves up TOTALLY different. SCT base files are setup on "load". I dont tune this way. I set spark curves so there is no way they will change based on load. Load tuning is dangerous in my opinion. Its a different opinion than most,but I have a track record of not blowing things up so I tend to think my way is the way to do it.
So,no two tuners are alike. Ask Jim Fitz, he went through 5 motors and his car was tuned by some of the best out there. Ask him how many motors he has gone through with me tuning it. The answer is zero."

Tim is reguarded as one of the best modular mustang tuners in the country....but maybe he didnt know about the issue at the time....it didnt show up on his low speed/part throttle testing while on the dyno. Apparently the actual weight of the car on teh engine, made this happen.