I've always been a little surprised my race tune (giac) wasn't really any faster than my pump tune. Now that I have a durametric and some data, I think I know why. With the race tune on 100 unleaded, timing is advanced, but it seems I'm closer to the knock threshold because the car pulls a lot more timing than when I'm on the pump tune. On average I think I'm probably running more timing throughout a pull on the pump tune. With the race tune I'll get somewhere in the 30's for timing, but then it will cut WAY back to low single digits. With the pump tune, I'll be somewhere in the 20's, but when it pulls back, it goes into the teens. So on average, while the pump tune doesn't advance as much, it's not getting pulled as much either.


So my question is, would I see an improvement if the timing on the race tune were pulled a couple degrees to prevent the ecu from pulling a lot timing? I'm sure there's other factors here I don't understand, but what do all you expert tuners say? Thanks!

 

Before trying to dial back the tune, try running higher octane like VP ms109 or Fuse Fuel 110 or 116 unleaded
100 oct race fuel is kind of weak and then when you add it to your tank, you are diluting it with whatever was in there already, effectively lowering the octane rating.

 

As I'm pretty new to the tuning thing I have spent a fair amount of time myself trying to figure this very same thing out.

My car is very low miles and has never had a tune nor any over revs. I have gone through the car and tested every aspect of the compression cycle. It runs very well and I'm currently running 7.6 60-130 on 93 octane. However what I have found is it's better to run less timing, than more and have the knock sensors pull it back to where it wants to be.

I've tried more aggressive timing with 102 octane and the car ran faster with stock timing.
I pbox every run as to compare every new map I flash.

I know for a fact you and I are not the only ones who battle this. I've heard of cars pulling all the timing from the car with the knock sensors.

Everything currently points to E85 as its proven to eliminate a lot of the knock and this allows more timing.

From what I've been told 1 degree of timing is 3-4 hp so that's pretty extreme.


When you say 30 degrees at what rpm boost and load are you running that at. I think people like to think of timing as a static values however there are a lot of variables that go into what timing your car is running at a given point.

A lot of people use 17 as stock timing and most stage 3 I believe add 11 more degrees. So is your knock sensors pulling you back to stock or past stock?

 

Also I would guarantee that the other companies such as GAIC and those that flash the ECU and do not provide a way of actively live time logging nor pulling logs are riding the knock sensors.

Those that look at logs every day will tell you every car is different and some for no real reason at all will only take so much timing. I can't imagine flashing on of these car with a generic map and assuming it's ruining as well as they are telling you it is.

That why I went with Cobb I can view all my real time data and Sam and Mitch can dial my car in to run the very best it can given my components and fuel. We are on V6 today of my pump fuel map I'm not sure how everyone else does it but Cobb reviews my actual logs and makes adjustments that are specific to my car.

It's a education thing. As more people get accustomed to interpreting and understanding their logs they will be better at taking care of their Mill and hopefully we see a lot less of them melting down.

 

Good point although I have been running 104 unleaded for several tanks and I think the octane and gas are good for my 100 tune.

 

I did a 3rd gear pull from 2000 rpm all the way to redline. Somewhere around 3000 rpm timing angle was around 30, then it dropped to single digits (3-4), then it was back up in the 20's, then dropped again, etc. It had 3-4 significant changes over the course of that one run, and yes I believe the sensors were pulling me back with less timing than stock.

 

That sounds a lot like your map was designed like that.
From what I have seen most maps pull timing around that 3500 RPM range as the Keep a lot of torque off the connecting rods.

However I can't speak as to why your knock sensors are so active

 

Seams like something is off. The tune should be great especially with those intercoolers. I would speak with Austin and see what he suggests. And logs

 

While I have a different motor, I noticed that on the GIAC tune, the race file needs really good race gas for optimization. There has been times when I actually ran slower on race than pump, but it was because my effective octane was somewhere lower than 100.

I know you said you are running 104 but sometimes gas goes bad...race gas is not immune to this. I would get some fresh pails of MS109 or Fuse 116 unleaded and make sure you are almost out of gas first. Then I would do a bunch of pulls on both race file and pump file and compare logs.

Best of luck and please keep us posted.

 

How are you blending your fuel? Most of our more hardcore guys are careful to get as much pump fuel out of the tank prior to adding the 100 octane fuel. If you're adding 5 gallons on top of 3 gallons of 93 octane, you're not really going to have "100 octane" fuel in the tank. Also, what type of 100 octane fuel are you buying? Not all are created equal. For 100 octane, I tend to prefer sunoco or trick over VP. If you're looking at the higher options, VP109 or sunoco 104 largely do the same things.

If you're seeing a large amount of timing correction, the car is plenty safe, but there is a good chance it might be actually making less power than the pump mode.

 

1 degree of timing is worth significantly more than 3-4hp. It depends on where you are in the rev range, but 10-15hp+ would be in the ballpark.

 

I can get on board with that line of thinking in the following scenario

Your IAT is up and your car is pulling timing and boost. Then your HP values might be correct.

However if you have two cars both running 22.5 psi one cars timing is 28 and the other car is 20 there will not be 120hp difference.

 

It's all cylinder pressure. Whether you get it with boost, higher compression ratio, ignition timing advance, etc. When you're near the limit sure, you're not going to continue to pick up power by adding timing. Using your example of 22.5psi and 20 degrees vs 28 degrees, +80hp isn't unrealistic.

 

Subscribed, I like the track this thread is on.


I have seen upwards of 46 degrees of ignition angle at the Road track (not drag Strip) with no knock.


Look forward to your findings.

 

I know you your not a fan of 60-130 times or dyno pulls. However 80hp would be 5-7 mph at the trap difference(1/4 mile) and pending all variables were the same almost a second difference.

I just haven't lost a second we are talking tenth with timing adjustments and some are sizable.

I too value ignition timing and want to give all the car will safely handle, and sure I'll leave a little on the table as to keep the mill fresh. And hell you may be talking 80hp idealistically and I'm talking 40hp real world and they might mean the same thing. I just have a hard ton be living 1 degree is 10hp to the pavement.

And naturally I've got a diminished return mentality. If we are going from stock timing to 8 degrees I'd anticipate 80hp or even 100hp. However as we get higher and higher up the ladder each rung is a little closer. As such you won't see those big HP jumps as you would coming off stock timing.

The reason why most guys use 3-4 as a rule of thumb as its a conservative average. I don't want to send the message hey we had to pull 5 degrees out of your car and they think they just lost 50hp.

Honestly with these cars the Knocks are going to pull it anyway so you never really had that 50hp