Timing question

[futurevr4man]

I am using a flashable chrome ecu for those that dont know. I have 1G heads on my 2G engine (2G wiring harness and car).

my question is: the timing reported by evoscan... is that accurate? what if i adjust the CAS sensor on my rear head, how does that affect the timing values reported?

i know a lot of people have reported timing drifts at higher RPM's with a 1G CAS/2G engine setup, and was curious what everyone thought about this?

[kywhitelightning]

Accurate, yes. Every load cell I hit has spit out the exact same timing number on Evoscan. Drifting due to CAS IDK.

Jeff

[Greg E]

If you installed the 91/92 photo sensor it creates a latency issue as the RPMs increase. Timing at idle will be about spot on, but the faster you rev the engine, the father off it becomes. Its usually off by about 4 degrees by redline.

People try to make a big deal out of this but the truth is, you can tune the engine around it just fine. Your numbers may be a little different than the guy who has an identical setup to you and running the 93+ haul sensors.

This latency isn't something you can see with evoscan. It can only be observed with a timing light.

[Greg E]

Wait, if you're running a 2G setup why is this a concern?

[Greg E]

Accurate, yes. Every load cell I hit has spit out the exact same timing number on Evoscan.

There are a few modifiers throwing in the timing calculation before final spark advance is sent to the PTU. Coolant temp, air temp, TPS tip in, idle.... The timing map is just the first part of the calculation. Many times your final advance will be a little different from the map due to these modifiers.

[futurevr4man]

greg, i have 1G heads, a 2G car/wiring/harness... that IS my concern. i want my car to run well, as expected, and reliably that way.

the drift is a concern for me, and im not sure if it runs more or less timing up top.

so the answer to my question overall is that the timing DOES drift with a 1G CAS sensor and 2G engine/wiring

[Greg E]

greg, i have 1G heads, a 2G car/wiring/harness... that IS my concern. i want my car to run well, as expected, and reliably that way.

the drift is a concern for me, and im not sure if it runs more or less timing up top.

so the answer to my question overall is that the timing DOES drift with a 1G CAS sensor and 2G engine/wiring

1G/2G heads don't matter. They are inner changeable.

If you're running 2G sensors, the CAS latency isnt even a discussion as you are running the exact same sensors as a 99.

If you are running a 91/92 CAS its still a non-issue as your tune will never "drift". You call for 22 degrees, you'll (consistently) get 18 at the plug. Its a non-issue because you'll be tuning timing for power. If the number 28 in the cell in the timing table gives you the best power then so be it. You'll consistently get the same spark time.

You're making a concern out of a non-issue.

[futurevr4man]

ok, that was much more clear. i guess i am too concerned with what the number that evoscan spits out, when i should just think of them as reference values. you can go higher or lower, it doesnt really matter what the actual number is, as long as i tune it for the best, safe, power output.

thanks greg.

p.s. i know the heads are interchangeable. i meant to refer to the CAS sensors, not the heads. my bad

[Chris@Rvengeperformance]

You can't mount the 2G cam sensor on 1G heads afaik.

Greg, it is likely the timing latency is just another table somewhere, right?

[futurevr4man]

that is correct, chris. i WANT to use a 2G cam sensor, but there is no spot on the heads... and they are DR stage 3's, so i cant just go pick another set up lol

[Chris@Rvengeperformance]

that is correct, chris. i WANT to use a 2G cam sensor, but there is no spot on the heads... and they are DR stage 3's, so i cant just go pick another set up lol

yeah the only thing that sucks is I know jrink did have some timing drift using the 1G sensor that was solved by using the 2G. It was at higher rpm and under a lot of power. I'd guess the timing belt was causing some "flutter". Probably nothing to worry about, but he did get more stable timing with the 2G sensor.

[Greg E]

You're right Chris. I forgot about the CAS mounts.

I found an adder value that's referenced right after the cam and crank sensor are referred in the code, however, this is for various timer functions. I haven't established a direct link for this adder value in its relation to timing and I'm hesitant to monkey with it out of fear of it effecting some other system.

I would need access to a 91/92 car (or one running the 91/92 CAS) with the flash ECU and a timing light for testing purposes.

[Chris@Rvengeperformance]

You're right Chris. I forgot about the CAS mounts.

I found an adder value that's referenced right after the cam and crank sensor are referred in the code, however, this is for various timer functions. I haven't established a direct link for this adder value in its relation to timing and I'm hesitant to monkey with it out of fear of it effecting some other system.

I would need access to a 91/92 car (or one running the 91/92 CAS) with the flash ECU and a timing light for testing purposes.

It is not something I would waste much time on, but I'm sure someday you'll find it.

[Greg E]

It is not something I would waste much time on, but I'm sure someday you'll find it.

Yeah, guys are more anxious right now for switchable maps and flex fuel capability.

Speaking of.... You're the only one with a running car right now. My 99 still needs a few more parts before I can begin reassembly. Do you have or know anyone with a front turbo exhaust housing with no stripped threads/broken studs?

[Chris@Rvengeperformance]

Yeah, guys are more anxious right now for switchable maps and flex fuel capability.

Speaking of.... You're the only one with a running car right now. My 99 still needs a few more parts before I can begin reassembly. Do you have or know anyone with a front turbo exhaust housing with no stripped threads/broken studs?

I wish I did, remember I spent a week drilling studs out of my 9b housing for the gray car.

Car is sitting out front right now, drives great. Warm restart is still rough, those changes I tried made it worse. I just haven't really logged it much on startup, need to check some more. Need to get my afr display in so I can see easier what it is doing.

Only thing I really miss is live tuning.

I was planning on trying e85 soon, but it drives so nice right now it is hard to make a big change :)

Depending on the damage to your housing I may be able to fix it. Can drill/tap or weld on it, whatever.

[smartaxel]

You're right Chris. I forgot about the CAS mounts.

I found an adder value that's referenced right after the cam and crank sensor are referred in the code, however, this is for various timer functions. I haven't established a direct link for this adder value in its relation to timing and I'm hesitant to monkey with it out of fear of it effecting some other system.

I would need access to a 91/92 car (or one running the 91/92 CAS) with the flash ECU and a timing light for testing purposes.

My car has a 93 engine with 92 wiring and CAS. It does have both the 93 sensors and the CAS. It will have the clone once Jester ships it.. So it may be running in the next few weeks pending no unforeseen issues. I'm not sure how close you are but I'm in Michigan.