I have a 1997 Z28 with a 383 ci LT1 engine built with a GM 847 cam, and I have been running an email tune on the car for a while now. This car was never meant to be a daily driver, but now that the fuel pump on my daily driver (1998 Z28) has gone bad, I have been driving the 1997 around town and noticed that the car runs really bad in stop-and-go traffic, with the car bucking severely at low RPMs (I have also had a minor vibration problem which I think is attributed to a tuning problem, but that is a different story and I have learned to live with it).

My question is, will a dyno tune improve the driveability of the car at low RPMs, or will the car act this way no matter how good the tune is because of the aggressive nature of the cam? The car ran good on the dyno with the email tune, so I just wanted to get some second opinions before I spend a good chunk of money on dyno tuning.

Thanks in advance.

-Fikret

 

An aggressive cam like that is going to buck no matter what at low rpms. You can probably have most of it tuned out but it will never be completely gone. If you want to use a dyno tune to improve the drivability of the car a load cell dyno is you best bet. Not an inertia style dyno such as a dynojet. A load cell dyno can actually put a physical load on the drivetrain replicating the car driving on the street.

 

Thanks for the response. I believe the shop that does tuning on LT1s around here uses a Dynojet, but they told me their dyno tuning includes driveability tuning which they do while I am driving and they are sitting in the passenger seat.

At this point, I am debating whether I live with the surging / bucking, get steeper gears to try to lessen it a bit, or get a smaller cam and get a proper dyno tune with the smaller cam in place. Or maybe I should buy the tuning software and learn to do it on my own...... How difficult is it to learn how to tune?

 

Your best bet would be to do some data logging and see what the car is doing before you go to the expense of putting in a different cam. I have this cam and tuned it myself without any issue and drives and idles just fine. What I find when I am tuning cars with larger cams is the idle air bleed hole needs to be enlarged. I also put my timing in the 34 degree range @ closed throttle. While I have an A4 with a big stall that eats up the cam surge, what i have as far as surge is very minimal if any. Being that you have a 383, that cam is considered smaller in that type of set up. I run it in a stout 355, so in mine it is considered large. I would find someone to log the car with a wideband driving around and tune it that way for good all around driving as oppesed to a dyno tune which most tune for peak power. This should provide good power across the board and better manners on the street.

 

Thanks. I did some research into self-tuning, and I think I am going to give it a try with Tunercat. I already have an interface cable and the software itself seems easy enough to use. I was thinking that the car needs a little more advance at lower RPMs, and possibly a little more fuel as well. I also see that there are a fair number of people that tune their own vehicles with Tunercat, so I hope to be able to use their experience to my advantage by asking questions.

 

I have a big cam with a manual and aluminum flywheel so I noticed surge, my surge was mostly fixed or greatly reduced by running open loop and speed density (removeing the 02's). No matter what I did the 02's made the engine run lean though they were not showing as lean.. it would run worse as time went on when the 02's were connected (02's were messign up the blm's and pulling fuel).

of course, the VE tables have to be spot on for SD with no 02's to run good.

Just something to think about.

 

fyi, I do have a m6 847 tune I did for some one in a 383 with ported heads. PM me an Email addy and I'll send you it.

 

Just sent you a PM, thanks.