dyno tuning results

[mikedsilva]

Can't believe I only just found this thread. Brilliant information, thanks.

[fred cook]

Originally Posted by targa72e

the next thing I decided to try changing was the cam timing. I started advancing the cam timing to see how it effected power. Each time I advanced the cam timing the torque and HP improved. In the end I ended up with cam timing just a little over the most advanced factory specs. I was worried about going to far and having the valves hit the pistons. Knowing what I know today I should have measured what piston to valve clearance I had and kept advancing until clearance got to small or I started loosing power. Below is a comparison from best run in first tuning and best after changing cam timing.





So from the start of this tuning I was able to go from 170 to 188 hp and 151 to 172 torque with out changing any parts.

john

Good info all! When I built my SC motor into a 3.3SS, I used 964 cams and set them right at the max advance point. I was assuming that the extra displacement along with almost 11:1 compression would make up the otherwise lost low/mid range torque and allow for good top end power. Turns out that is exactly what happened. Sometimes it is better to be lucky than good!

[jjeffries]

This thread is also new to me, and fascinating.

Question for the Knowledgable: In this series of graphs, when the OP went from his 3.2/digital F.i. back to CIS, are we seeing that the CIS yields more torque and power in the ca. 3500-4500 RPM area? If yes, is that the kind of thing which can be overcome/improved upon in the digital set-up by tuning for better mixture and/or timing values in those specific areas of the RPM range?

Thanks to the OP for this format, very educational.
John/CT

Originally Posted by targa72e

As I was doing more DE events I decided to take my car back to stock and reinstalled the factory CIS. The CIS is not nearly as good as the 3.2 manifolds. Below is a graph after I reinstalled the CIS and tuned.



I was sad about the power loss going back to CIS.

john

[targa72e]

Yes, the CIS made better power from 3.5-4.5K. I don't know for sure but my guess would be it is probably due to the CIS runners being smaller than 3.2 manifold runners and the air flow not being large enough for the CIS plate to restrict power. It would be interesting to see someone who did the BLITZ EFI system with CIS runners and then switched to 3.2 Carrera manifolds to see what the difference looks like.

john

[VFR750]

How much cam timing did you go to?

This is very cool. 1982 stock cis was 1.6mm

I’m curious as to how far you went to get such a nice improvement.

[targa72e]

The cams were installed at the most retarded factory spec. I started advancing the cam timing to see how it effected power. Each time I advanced the cam timing the torque and HP improved. In the end I ended up with cam timing just a little over the most advanced factory specs. I was worried about going to far and having the valves hit the pistons. Knowing what I know today I should have measured what piston to valve clearance I had and kept advancing until clearance got to small or I started loosing power. I had some friends that changed there cam timing to most advanced spec with similar results (all 78-79 big runner/port engines).

john

[mikedsilva]

Originally Posted by targa72e

The cams were installed at the most retarded factory spec. I started advancing the cam timing to see how it effected power. Each time I advanced the cam timing the torque and HP improved. In the end I ended up with cam timing just a little over the most advanced factory specs. I was worried about going to far and having the valves hit the pistons. Knowing what I know today I should have measured what piston to valve clearance I had and kept advancing until clearance got to small or I started loosing power. I had some friends that changed there cam timing to most advanced spec with similar results (all 78-79 big runner/port engines).

john

Hi
when you did advance the cam timing, did you pull the engine each time? Did you have to pull all the rockers except cyl 1 & 4?
Reason I ask, is I am tempted to do something similar..

[TimT]

when you did advance the cam timing, did you pull the engine each time? Did you have to pull all the rockers except cyl 1 & 4?

You can fiddle with the cam timing with the engine in the car... its a bit of a PIA, don't have to remove the other rockers, just back the adjustment screws all the way out on the rockers

BTDT at the track at 2:00AM

[PeteKz]

Like others have said, I just found this thread. Great work, Targa72e, and thanks fore posting the dyno graphs. I've had way too many arguments with people who didn't have actual data to back them up. This is about as good as anyone could ask for.

I also have adjusted fuel distributors on other CIS cars to get equal output at each injector. It appears to also make the engine run smoother.

Pardon me while I run out to the garage and advance my cams...