What IAT2 to start pulling timing? TVS with 2.8", 93 plus booster.

[TheFleshRocket]

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I have one primary question. Read everything below if you like, but I primarily want an answer to the following question:

Those of you with TVSes running 93 octane, at what IAT2 does your tune start pulling timing?

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I'm trying to determine how the timing is set up on my recently-upgraded-and-remote-tuned TVS-equipped Cobra. I/C and H/E system is all stock, running 70/30 water/coolant, with Water Wetter. It's running a 2.8" upper pulley (boost peaks at 19 PSI, then drops to 18 PSI close to redline), and I'm using 93 octane plus a pint of Klotz octane booster in each tank.

Here are some test results using an OBD2 scan tool:
2nd gear, 3250 RPM, 117F IAT2, 16.5 degrees (pedalled it to WOT due to traction issues, start of pull)
2nd gear, 6000 RPM, 120F IAT2, 16.5 degrees
3rd gear, 6000 RPM, 129F IAT2, 15.0 degrees
4th gear, 6000 RPM, 142F IAT2, 14.0 degrees
(IAT1 was around 75, and ambient was in the mid 60s.)

Seems pretty obvious that the tune is pulling timing as the IAT2 readings increase.

I've read that the factory tune starts pulling timing as low as 100F, and that it's based on some sort of setting of timing retard at 150F. So, the tune specifies at what IAT2 reading timing should start being pulled, and then specifies how much timing should be pulled at 150F IAT2, and the computer interpolates between 0 timing being pulled at 100F IAT2, on up to xx timing being pulled at 150F IAT2. So, hypothetically, if it pulls 10 degrees at 150F, it would pull half that timing at half that temp difference, so 5 degrees being pulled at 125F. Someone please correct me if I'm wrong.

I don't know if 16.5 degrees is the "no timing pulled" setting (like, maybe it doesn't start pulling timing until beyond 120F), or if it's already been pulling timing as low as 100F. I'll try to do a pull tomorrow morning, when the intercooler coolant is (hopefully) still below 100F, and see what the timing is. However, since it's obviously pulled 1.5 degrees of timing between 120F and 129F, it's definitely started pulling timing somewhere between those temps.

Also from my reading, tuners generally raise the floor at which the ECM starts pulling timing, but I haven't found any consensus.

So, at what IAT2 reading should the ECM start pulling timing?

How much timing should be pulled at 150F IAT2?

Here's a link to the video: http://www.thefleshrocket.com/images/cars/cobra/videos/IAT2_monitoring_pull.m4v
Here it is on Youtube, but it's only at 360P quality--not sure why:

 

[TheFleshRocket]

This morning, with the coolant between 180-190 (190 is when the high speed fan kicks on, and it never goes higher than that; stat is either 160 or 170, I forget) just a third gear pull:
3rd gear, 3000 RPM, 95F IAT2, 15.0 degrees
3rd gear, 6000 RPM, 97F IAT2, 16.0 degrees

For whatever reason, "base" timing was only 16.0 degrees today, when it went to 16.5 degrees yesterday. But it does seem like 16.5 degrees is the most advanced that the timing will be, so presumably it starts to pull timing between 120F and 129F IAT2.

So, at what IAT2 should it start pulling timing? I'm thinking 140F.

 

[whitedevil95]

Why dont you just ask your tuner what he has it set for?

 

[Soap]

Why dont you just ask your tuner what he has it set for?

Same thing I was thinking. You are doing a lot of guesswork when the full answer is a simple question away.

--Joe

 

[TheFleshRocket]

I think you guys misunderstand--I'm not asking you to help me determine what the values are set to now. I have a pretty good idea that timing starts being pulled when IAT2 is between 120F and 129F, and given the rate of timing being pulled, it's pulling 3.0 to 3.5 degrees by 150F.

What I'm asking is, what SHOULD those values be set to? At what temp should the ECM start pulling timing? Is it safe to run max timing at 140F IAT2? How much timing should be pulled at 150F IAT2?

Basically, my tuner seems a little hesitant to provide actual values of what things are set to, but he'll make the changes that I request of him. I'd like to know specifically what I want before I contact him again.

 

[Soap]

It all depends on what fuel you use and how your timing is set. There is no set answer for this, it's just whatever keeps the engine from detonating.

--Joe

 

[c6zhombre]

There is no cookie cutter answer.....otherwise we would all buy preset "canned" tunes for a given setup of parts. Every car is a fingerprint and could require slightly different changes to the tune. That's why you need a true wideband a/f reading along with all the other pids a tuner will require. "Custom" tune.

Do you have a wideband that you are logging? If you don't, you are flying blind and not giving your tuner the most critical data point of all.

 

[TheFleshRocket]

It all depends on what fuel you use and how your timing is set. There is no set answer for this, it's just whatever keeps the engine from detonating.

Yeah, I understand that, but surely there is a common IAT2 reading at which most tuners consider safe to have time start being pulled. Do most tuners start pulling timing at 130F? 140F? 150F?

 

[TheFleshRocket]

Do you have a wideband that you are logging? If you don't, you are flying blind and not giving your tuner the most critical data point of all.

AFR is solid in the mid 11s across the board at WOT. Full data logging has been done and the tune adjusted accordingly.

I just feel like pulling timing between 120-129F is too early and want to know what a commonly-accepted IAT2 reading is for timing to start being pulled.

 

[TheFleshRocket]

Perhaps I should have phrased this whole thing differently. Forget everything I've posted thus far, and answer this:

Those of you with TVSes running 93 octane, at what IAT2 does your tune start pulling timing?

 

[gt347mustang]

AFR is solid in the mid 11s across the board at WOT. Full data logging has been done and the tune adjusted accordingly.

I just feel like pulling timing between 120-129F is too early and want to know what a commonly-accepted IAT2 reading is for timing to start being pulled.

Without combustion analysis software using cylinder pressure sensors this is impossible. Next best solution is tuning it on a dyno at different IAT 2 temps.

Don't try to look for somebody to spout out numbers, it's not going to happen, and even if they did it won't be valid for your combo and it's likely not even going to be right.

 

[TheFleshRocket]

Without combustion analysis software using cylinder pressure sensors this is impossible. Next best solution is tuning it on a dyno at different IAT 2 temps.

Don't try to look for somebody to spout out numbers, it's not going to happen, and even if they did it won't be valid for your combo and it's likely not even going to be right.

I would agree with you if I was attempting to tune this to the ragged edge. I am not. My tuner has been VERY conservative and I am confident that more is left without getting anywhere near the danger zone.

There are dozens of remote tuners, all of whom pick an IAT2 reading at which to start pulling timing, none of whom are relying on cylinder pressure sensors to come up with the setting.

I realize that I gave WAY too much information in my first post, but I don't understand why you guys are making this so complicated.

 

[gt347mustang]

I don't understand why you guys are making this so complicated.

Because the answer is complicated.

You sound knowledgeable enough to tune it yourself. Give it a shot. Once you dig in you'll realize the answer isn't as simple as you think.

Have you pulled your plugs? How do you know it's conservative? Why don't you just tell your tuner to add timing. I mean, that's the whole point to this thread right? So you can justify telling your tuner how to do their job... I can see the thread now: "remote tuner blew up my termi!!! Halp"

The fact that you're street tuned remotely tells you're not overly serious about how fast your car is. Trying to squeeze every little horsepower at hot iat's is an easy way to hurt something.

Why not just get a better heat exchanger to help with iat?

 

[TheFleshRocket]

Have a look at these posts (and read the whole thread):
High boost TVS guys in here please
High boost TVS guys in here please

It's been shown that the IAT2 sensor mount on the TVS blower keeps the sensor too far out of the airstream, and that heatsoak causes the sensor to read inaccurately high. Additionally, IAT2 readings climb inaccurately quickly during pulls. The OP (well heck, it's Soap and he's in THIS thread!) milled down the IAT2 mounting location on the TVS so that the sensor sat better in the airflow and noticed lower IAT2s and less IAT2 climb during pulls.

If, for example, the IAT2 reading in fourth gear really was 140F, it might make sense to be pulling timing at that point. But if the IAT2 sensor was reading high due to its insufficient depth into the airstream, then the tune should be reconfigured to not pull timing until a higher temperature to compensate.

To answer your question, no I have not pulled the plugs. There has been no audible hint of detonation (I realize that doesn't mean that it doesn't exist), but given that my car's timing (16.5 degrees, 2.8 pulley, ~96 octane) is more-conservative than what many others have posted (17-18 degrees, 2.8 pulley, 93 octane, seems to be pretty common), I don't have reason to think that there is any detonation.

I do plan to get a better heat exchanger, but I am also suspicious that it won't help the IAT2 readings much if the sensor is already reading inaccurately.

I am not "trying to squeeze every little horsepower", but I am trying to get it close to 600rwhp, when right now, seat of the pants says it's probably around 560-570 before it starts pulling timing, and 520-530 once timing is being pulled.

I closely monitor my engine parameters at all times, and especially after loading an updated tune. I am confident that my tuner would not inadvertently make a dangerous change, and I'm also confident that I'd discover it before anything bad happened. And if I did hurt the motor, I know it's on me and nobody else.

At this point, it's been long enough since I've done the blower swap that I am almost considering pulling it to have the IAT2 sensor mount milled down. Either that, or just telling my tuner to make the tune not start pulling timing until 150F and then listening and checking the plugs for signs of detonation (since I can't seem to get any sort of straight answer).

 

[cj428mach]

I think for the most part tuners leave the timing retard for IAT2 tables stock when on gasoline.

Its also been a long time since I've looked at the tables but I believe they pull timing starting at 110 degrees. Also FYI the table doesn't have to be linear. The tuner could set the tune to pull 1 degree of timing from 110 to 140 degrees IAT2, then pull 15 degrees of timing from 140 to 145 degrees IAT2.

Don Lasota's book says that when tuning an 03-04 Cobra the max timing at 18 PSI is 17 degrees when running 93 octane. So most would set the max timing at 17 and let the stock IAT2 do their thing.

 

[TheFleshRocket]

From what I recall reading, the stock tune starts pulling timing when IAT2 is 100F--ridiculously low.

I wish I'd datalogged my Cobra when it had the 2.76 Eaton installed. It pulled hard and didn't seem to heat soak or noticeably lose power when hot. It had a tune from RWTD, and unfortunately, that company fizzled out around 2011 so no way I can ask them how they had the timing pulled.

 

[c6zhombre]

From what I recall reading, the stock tune starts pulling timing when IAT2 is 100F--ridiculously low.

I wish I'd datalogged my Cobra when it had the 2.76 Eaton installed. It pulled hard and didn't seem to heat soak or noticeably lose power when hot. It had a tune from RWTD, and unfortunately, that company fizzled out around 2011 so no way I can ask them how they had the timing pulled.

You're running 19psi with the tvs. The 2.76 upper what, maybe 12-13? Its apples to oranges.

I recommended this on your last thread....and I'll do it again....re pulley the tvs for lower boost. 19 is too much. Pulley down to 15-16, create less heat, retain more usable power for the real world. Your tuner is probably doing a fine job....I think your expectations for 19psi repeated all day performance are unrealistic. What you really need is E85 if you want to limit IAT2 limitations

 

[TheFleshRocket]

pulley the tvs for lower boost. 19 is too much. Pulley down to 15-16, create less heat, retain more usable power for the real world. Your tuner is probably doing a fine job....I think your expectations for 19psi repeated all day performance are unrealistic. What you really need is E85 if you want to limit IAT2 limitations

I get that the Eaton to the TVS is apples to oranges, but I'm still curious.

I do plan to get a 3.0 pulley, which VMP says should be 16-17 PSI, as well as an upgraded heat exchanger. (There do seem to be a lot of people running 2.8 pulleys on 93, though.)

To be clear, I'm not even looking for "repeated all day performance", I'd be satisfied with timing not being pulled unnecessarily during a single run. The tune pulled 2.5 degrees of timing during a single 2nd-4th gear pull on a non-heat-soaked engine.

 

[cj428mach]

AFR is solid in the mid 11s across the board at WOT. Full data logging has been done and the tune adjusted accordingly.

I just feel like pulling timing between 120-129F is too early and want to know what a commonly-accepted IAT2 reading is for timing to start being pulled.

Heres a good thread with some IAT2 info.

https://www.svtperformance.com/forums/threads/lets-talk-iat2.1017427/

I see I posted that Don Lasota (the guy that writes the tuning manuals a lot of people use) says that at 150 degrees you're probably getting detonation even if you can't hear it. So the stock table is probably about right.

 

[TheFleshRocket]

Lots of good reading in that thread. Thanks!

This picture was posted, which shows 100F and 150F as two of the points between which the PCM interpolates to determine how much timing is pulled. Can 100F be changed to something higher, like 130F, so that no timing is pulled due to IAT2 below that value?

https://www.svtperformance.com/forums/threads/lets-talk-iat2.1017427/page-2#post-14204127