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Drag event...


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roppa440

Club Member

Tue 31 Jul 18 08:25

Re: Drag event...


Pinhead wrote (View Post):roppa 440

I think I have read that you have not had the car tuned for the bolt on mods you are running



I don't have any bolt on engine mods. Except for headers.


All I have done is improved the airflow into and out of the engine. Just some mild porting of the throttle body, MAF sensor, and head ports. I am also running it 10 degrees F cooler.


I am running a bone stock Diablo tune for a bone stock version of my car (15hp is all you can squeeze out this way) and, when I have studied the data logs I have recorded, everything is spot on. Fuel trim is minimal. Not effected by the headers at all. I'm running a more aggressive ignition curve from the Diablo tune anyway.


I really do not want to throw money into the car to gain more power. Been there and done that in the past. This was an exercise to get as much out of the stock engine parts as I personally could myself. Just to keep my hand in so to speak. Wink



Last edited by roppa440 on Tue 31 Jul 18 08:28; edited 1 time in total. [2 %]

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Pinhead

New Comer

Tue 31 Jul 18 13:44

Re: Drag event...


That's all great
The tune is not to make it more powerful but to make it right this has a side affect of a little more power you are quite right in that it does not need doing as the ecu is very adaptable and will always keep the engine on the safe side

I personally think the stock ecu is quite aggressive with timing anyway you usually find that they blend the high and low octane tables on a bone stock engine due to kr I pulled timing out of mine with just headers and ls6 intake and it ran better you actually run more timing this way as kr pulls timing very aggressively the ecu learns this and runs timing that will prevent kr again

Are your long term fuel trims positive or negative I know you said they were minimal but I would be interested to know which way they are

What you have done to your engine is all really good and they respond well to it as you have found out

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roppa440

Club Member

Tue 31 Jul 18 23:17

Re: Drag event...


Pinhead wrote (View Post):

Are your long term fuel trims positive or negative I know you said they were minimal but I would be interested to know which way they are

What you have done to your engine is all really good and they respond well to it as you have found out


Long term they are still neutral. Just vary slightly within normal parameters.

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Pinhead

New Comer

Thu 02 Aug 18 09:57

Re: Drag event...


Long term they are still neutral. Just vary slightly within normal parameters.[/quote]


That's perfect then ideally you want them at zero or slightly negative
Positive fuel trims are not good because it puts extra fuel in when in PE mode and this makes them run rich at Wot

Are you going to this straightliners drag event in September it's at this new track somewhere near newcastle

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roppa440

Club Member

Sat 04 Aug 18 17:13

Re: Drag event...


Weather permitting yes. I think its on two days though so will have to decide which one.



Last edited by roppa440 on Sat 04 Aug 18 17:14; edited 1 time in total. [2 %]

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roppa440

Club Member

Sat 04 Aug 18 17:17

Re: Drag event...


Might be going slightly positive on the trim. I can't remember which side it swings to slightly. I will have to recheck the logs.

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roppa440

Club Member

Mon 13 Aug 18 08:44

Re: Drag event...


So I was checking over the weekend to see if the fuel trim was going negative (it is) but also to see why I had a fault code on cat converter inefficiency pop up the other day.

It looked like the Cats are not working. Rear O2 sensor voltage was swinging all over the place.

But these cats are only 7 months old.

Then I decided to data log for misfires. OMG. Starts off OK and then more and more cylinders start misfiring. So not the cats faulty at all it seems.

Now the spark plug leads are not very old either. But when I had the headers made in January they broke a couple pulling them off and had to replace them.
The only two not showing signs of misfire are the two they replaced...

It is funny because I did "feel" the engine was firing unevenly but put that down to the sound of the stainless headers. But it looks like it actually is.

So new plug leads are on order.

The good news is that 12.95 I ran into the headwind at SPR was done with not all cylinders always firing.......



Last edited by roppa440 on Mon 13 Aug 18 08:45; edited 1 time in total. [2 %]

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roppa440

Club Member

Mon 13 Aug 18 09:20

Re: Drag event...


It's pretty bad when you look at the O2 sensor voltages.

Pre-cat sensor voltage (blue) should be a regular wave I think? Post cat voltage should be a level 0.5v.

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Pinhead

New Comer

Tue 14 Aug 18 20:48

Re: Drag event...


The o2 sensors are quite unreliable and the extra heat from headers don't help
The fact that they are switching says they are not in bad order they maybe getting slightly lazy but I would try and cure the misfire first as the ecu will be trying to work round it and it will be all to pot
Are you using wire extenders? These can cause more problems than they solve
I am not sure about fitment issues with headers on c5s but on the f body they sit really close under the floor and can hit under acceleration the knock sensors picked this up on mine and it caused havoc it was cured with poly motor mounts

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Pinhead

New Comer

Tue 14 Aug 18 21:15

Re: Drag event...


Just pulled some old log files up from tuning my car to look at the 02 wave form for comparison
They are slightly more wave like but big but
I have a very fast data collection rate at 10 frames per second so it may just be how fast your scanner can see them
They are certainly not uniform
I don't have rear o2s I have used the wires for the fronts and changed the pins in the plug at the ecu and deleted the rears in the tune

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