engine detonation problem

[jeeping99tj]

Hey everyone! I jus finished my first motor build and my only issue now is detonation. I am running the la3 comp. Big vam. Top mount intercooler. Gutted upper. Knife edged lower. Mild ported D port head. A237 cam. Esslinger adj cam gear. 3" exhaust with magnaflow. 35 lb injectors. A adjustable fpr. Ported E6 and t3 with .60/.48 turbo. LC1 wideband. I have a walbro 255 I still need to install. But my problem is in 3,4,5 I get some bad detonation above 3k. It seemed to do a lil better when I switched to NGK tR6 plugs but it seemed to come back. I got my cam at around 6* and my ignition timing around 10* when I'm cruising my A/F is at 14.4ish and under full boost its around 10-12. I got boost set to 18 right now but still noticed it at 15-16. Kinda giving up on it. Might mess with the timing a lil but not sure what else to do. My fuel pressure is set at 39 at idle.

[RatFink]

Nothing looks to be wrong with your setup. does the intercooler get air circulation? Did you throw the intake air temp sensor in the intake with the ECU swap? I am assuming you Grounded the "premium switch" wire, have you tried un-grounding it? I would not drop the timing below 10* I have always been able to run 12-13* base timing with no problems on even with A little hotter TR5 plug. You may want to Zero your cam out and make sure the timing is all good too.

[jeeping99tj]

I don't think It had a permuin switch. And ill recheck timing I had to do the string method to time for now and at dead on 0 the revved real slow. So pretty sure that's most my problem. Will any 2.3 timing cover work?

[jeeping99tj]

And I know my ecu was repinned by some Ian potter but not sure where sensor would be.

[RatFink]

Ok, the LA3 was a later 32 bit processor as opposed to the XR's 16 bit. The LA3 was much more powerful and had more inputs. One of which was an intake air temp sensor the XR's never had. Sensor goes in the lower intake manifold air stream from the factory. The TC's also had a "Premium switch" which changed the timing strategy in the ECU, but most people ground it, so it's perminently on.
The LA3's also had a heated O2 sensor from the factory as opposed to the XR's single wire O2.
I would try to search around as well as figuring out what Re-pinning Ian did.
And get yourself timing pointer like this for Christ's sake. I didn't even realize you didn't have the crappy little plastic thing on there or that would have been my first suggestion.
http://www.mc2racing.com/products/xr4ti ... index.html

[jeeping99tj]

Ok ill do a li research on the ecu. I bought the car and had all this stuff done I jus rebuild the motor and hoped it all was right and was missing the junk cover.

[Ray]

Is your cam advanced 6*?

First check to make sure it has the IAT and Premium switch hooked up.

Then i'd back the cam timing down a few clicks - start around 0, then go from there. More advance brings the load to lower RPM, which seems to be where you're having trouble.

Other quick fix - plug the knock sensor in.

[jeeping99tj]

I talked to the guy I got car from and he said the premuin switch should be grounded internally and the iat isn't needed. I got the stock xr lower so pretty sure I don't have one. The cam is a esslinger old style. Says mark = 2* so I'm at like 3-4 lines. That to much? I'm getting a timing cover later today and retiring. Need to find out who the ian potter guy is. His name is on ecu and its writing what pins were moved

[hEaT]

If it's Ian's ECU than the switch is internally grounded and no IAT is needed.


Reset your cam timing to 0*, verify it is truly zero by matching it with the crank and verify your ignition timing again.

The XR lower does have a knock sensor, it sticks out towards the wheel and you should keep it plugged in if you're hearing some knock.

Stupid mistake, I ran my car at 26* base....and with the knock sensor plugged in, it never pinged.

[jeeping99tj]

And another weird problem is my tach. Idk if its bad but I have never seen it above 5 k. So I bought a stewart warner tach and hooked it to neg coil wire and set shift lite to 4500 and has never lit up and I don't think its my tach. Seems to rev decent with cam advanced but prolly leaning toward another timing issue ?

[Ray]

with the cam that far advanced the car isn't breathing as well up top, meaning you're shifting your power to the 2800-4k range, so you might not need to go above 4500.

like we said, try to set the cam to 0 and see what happens.