I was wondering if anyone has any luck tuning a 350 TPI with the Xtreme energy 262 cam? I have this setup with 24lb injectors and am having no luck with my current bin. I basically just changed the injector constant from stock to the 24lb as of right now. The IAC is surging back and forth when closed loop hits causing the RPM's to go up and down during idle and cruise. It ends up leveling out after about 15 miles of cruising, but has no power. Any suggestions?

that isnt really a big cam for TPI so i would think it would run just fine on stock programing with only mild changes made

what ECM you working with? MAF or SD?

Whats your base timing on that motor? I'd leave it at around 8 degrees base timing. change the chip timing to 8 as well and add 2 degrees to the whole table for starters. maybe try making max timing come in sooner. i think stock injectors would have been just fine but 24's is a nice upgrade.

try cleaning out the IAC motor and then resetting it. Could be dirty, my L98 was doing that and it was a dirty IAC and throttle body.

Then look at your fuel at idle, it may be abit rich with the cam now so take some fuel out.

Yeah,
I didn't think it would be an outrageous cam for it. I am running speed density on it. I am a little stumped on my base timing though. When I put it to 8 it is an absolute dog and doesn't run correct at all. I have it upwards of like 16 or so. It is almost like the dist. is off a bit. The chip is still stock timing though. As far as the IAC goes it was sticking so I went through and cleaned it out already. Right now I am running about 50 for fuel pressure. Whenever I check the plugs they always look like it is running lean.

i run MAF so i dont know much about SD. but 16 base timing does seem way too high for that cam.

hopefully someone else will get in here with more knowledge on this subject

16 for the base timing does seem high to me as well. the weird part is as I increase the timing it seems to run better.

Did you disconnect the ESC when you set the base timing?

Yeah, I disconnected the esc when I set the base timing. It was almost as if my distributer is off one notch because at 6deg the hei was maxed out against the intake. That was as low as I could go for timing.

Sounds like your IAC is not properly adjusted for your Idle. I have found it best to adjust the IAC to approximately 50 rpm less than the "fully warmed up" idle rpm.

As most people increase th idle rpm for bigger cams, they MUST adjust the IAC to a higher rpm than the stock setting or they will encounter "hunting and surging" just like you are experiencing.

So, if you minimum rpm is 750 rpm (when fully warmed), adjust your IAC to 700 rpm.

If you are not familar with how to reset the IAC, go the FAQs. There is a great description on the procedure to adjust the IAC (other than what rpm you should adjust it to....but I just did that).

Good luck.

Also, FORGET adjusting the spark by twisting the distributor. You MUST adjust the spark within the Prom AND you leave the distributor at the stock setting.

Your spark is WAY TOO HIGH at 16 degrees. These engines are highly prone to knock (though you may hear it). Adjusting the spark that high just results in the ECM pulling all that spark (plus more) than you adjusted it and makes it slower.

When properly tuned, the typical L98 can't handle more than 25* in WOT for total spark advanced. Only when you do a complete rebuild with different heads will you be able to handle more spark...and then it still may not mean you are making more power.

The trick with tuning is to make the maximum amount of power with the LEAST amount of spark. I would rather leave a couple HP with less spark as detonation, even if inaudible, will result in less durability in the long run.

It sounds like you are trying to tune with "mechanical methods"....and on these EFI cars, it just doesn't work. Forget the "old school" stuff.

Thanks for the response, it is great input for me. I will turn the timing back down at the distributer. I also will try and readjust my IAC again.
As far as the engine goes, it does have different heads though they aren't outrageous. They are just the old camelback heads.
When adjusting the spark in the prom, should I start only with adjusting the base timing setting or is there another one I should look at changing as well? Should I do this before or after IAC adjustments?

For the initial timing, set the distributor to 8 degrees BTDC, then set that same value in the BIN. They should match up. The base timing is where the engine will crank at.

Then for timing changes tweak the main SA table(s)

With the cam additional timing will be required at lower speeds, self-EGR, lower cylinder fill and all that.

RBob.

Eh, well RBob posted while I was typing and said the same thing I was going to say, so...never mind this post.

Looks like I am going to have to read up on timing tweaking. Is there really any good place to start with the timing tweaks for having a little bit of cam? Maybe a bin to compare to? I am not using the AUJP bin yet. Probably should start there.

With the cam the lower RPM/MAP areas can take additional timing. How much depends upon several factors. Try more (or less) in areas and see how it drives. Take notes.

Also, read a data log of normal driving such as pulling out. Note the path the RPM & MAP takes as the go-pedal is depressed. This is the same areas of the VE & SA tables that are being traversed.

Think of SA as torque, more is more torque, less is less torque. For driveability sometimes less SA in an area is better. Can make the engine speed easier to control.

RBob.

Well guys,
Here is what I have got. I finally got my ALDL cable and was able to hook up to the computer. I loaded the AUJP bin and adjusted it for 8 deg for timing along with my car. I then reset the IAC and adjusted my idle to about 700rpm. I say about because my stock tach went bad so I have no real reference yet. I went by ear. I datalogged the results in tunerproRT. I see that my TPS is a little too high. The car is real weak right now and throttle response is horrible. What do you guys read out of the datalog besides the TPS being high. Could that be all of the problem. It is at .67 at idle. The whole datalog is at idle for that matter.

any chance that the harmonic balancer's elastomer/rubber band has rotted allowing the outer metal ring to slip and is messing with your timing readings? and/or that the cam was not installed straight up or may be a tooth off itself?

I had been thinking that same thing for a while with the harmonic balancer. I had no real way of telling without installing a new one. I did adjust the TPS down to .5 last night and it made a world of difference for the throttle response. I need to road test the car yet and I will do another datalog. I will keep you all posted.