03 Cobra Tuning - Turbo vs PD Supercharger

[fbody83]

A friend of mine is working on picking up a twin turbo 03 cobra that's currently tuned on 60lb injectors and 93 octane. He's going to put bigger injectors and run e85 in a few weeks. I've successfully tuned my 03 cobra via PRP which has a 2.9 whipple, custom cams ID1000's and E85.

I'd like to give his a shot and I would think that the tuning between the two cars won't be too different except for MAF and spark. My main question is related to the spark table - On an 03 cobra with a PD blower, boost is instantaneous so at WOT in the lower RPM ranges, it's a good practice to keep timing low and ramp it up as RPM's increase. In a turbo car, is it common to do the opposite to help the turbo spool faster? For example, get more aggressive with timing in the lower RPM's as the turbo is trying to spool and then bring spark down a little bit once it hits boost?

Any other best practices or tips for tuning a turbo cobra?

Thanks in advance.

 

[decipha]

few tips about boosted 4v in general

first off they do not like compression, so if its a high compression boosted 4v then you need to yank the timing way down at peak tq or it will detonate. I have yet to ever tune a 4v that wanted more than 8 deg of timing at peak torque when boosted (w/ up to 12lbs of boost at peak tq)

I've never tuned a boosted 4v that's ever wanted more than 20 deg of timing up top including bone stocker's

the older b heads typically like a couples degrees more than the c heads, for reference n/a on b heads i usually shoot for 27 degrees, n/a on c heads (low compression) i shoot for no more than 23 degrees. C heads with high compression they never want any more than 16 deg at peak tq naturally aspirated (think marauder and mach 1). The b heads for some reason seem to be less temperamental to higher compression than the c heads for some odd reason.

the cobra 4v's want a lot of dashpot for best driveability, i recommend setting the min dashpot and min idle correction MPH scalars to 25 for both - as is stock on the cobras.

the 03 cobra has the fastest of the eec-v processor speeds. As such, the highest injector slope value the code can calculate is 0.0167 although you can stuff a higher value than that in the software the ecu code will clip it to no higher than that value. So be sure you scale your tune back far enough that its below that.

regardless of n/a turbo or blower you should always scale your table's load axis accordingly to give yourself the most resolution. At 0 vac / 0 boost be sure you don't exceed MBT. Then linearly reduce it from there. If done correctly you'll see that it doesn't matter if its a turbo or a blower, a turbo can't reach those higher load values at a lower rpm so it will have more timing than a blower that makes more boost down low.

remember, the ecu "see's" boost as load. So know where your 0 vac / 0 boost load value is throughout the rpm range.

I know this goes without saying but don't forget to let the turbo cool down after making a pull. Don't just make a hard pull and shut the engine off. Let it run for a bit to cool the turbo down before shutting her off.

btw, sct is pretty outdated when it comes to the EECs. Its much easier and faster to do realtime tuning using a moates quarterhorse. It saves a bunch of timing being able to write tune changes while the engine is running rather than that archaic method of flashing with the handheld. Not to mention the custom tuning software for the 03-04 cobras is free for the QH.

 

[WaffleMan]

I have yet to ever tune a 4v that wanted more than 8 deg of timing at peak torque when boosted (w/ up to 12lbs of boost at peak tq)

I've never tuned a boosted 4v that's ever wanted more than 20 deg of timing up top including bone stocker's

Can you elaborate on this more? I’ve seen a post where you told a e85 Eaton Cobra to run 27* at wot from 3k-redline. Also on your site you have 20* for MBT on a boosted 4.6 4v C head and 24* n/a. 8* seems extremely low, and if so I had my e85 tvs setup extremely over advanced hitting around 20* at 3.5k and ramping to 23* by 6500.

Link for the thread that you recommended such high timing, post 7: https://www.svtperformance.com/forums/threads/timing-ramp-eaton-e-85.1084816/

Link to timing on website: MBT Reference Chart / EFIDynoTuning

Thanks

 

[decipha]

you cant directly compare completely different setups

e85 is completely different than pump gas

yes i shoot 27 degrees or so to 4vs on e85 on lower boost levels < 15 lbs or so on higher boost 25+ i usually dont exceed 20-23 depending on amount of boost and how they want it

correct, 20 deg is usually all a boosted 4v wants on pump

8 deg is at peak tq, nothing to do with timing up top, the 4v engines dont like alot of timing at peak tq, Ive taken them from 8 deg to 24 deg at peak tq and it not make much of a difference. The 4v engines also are not tolerant to high compression at all. The higher the static compression the less timing they want.

I have a post on the efidynotuning forum with good info, search for mach1