Well, I didn't want to be "that guy" but...I need some help tuning my pride-n-joy. I have a 1995 Cobra that has been heavily modified without proper engine tuning and (of course) she's not running 100%; doesn't idle well, is sluggish to respond, and not as powerful as a 331 cid should be. I recently purchased/installed a Tweecer RT module and have ordered a dual FAST wideband kit that will be installed soon. I am relatively new the wide-world of EFI tuning and would appreciate some advice/guidance from the EFI guys out there - specifically tuning for idle (for now).
To get the engine mods out of the way and let you know what we're dealing with, they are as follows:
• Forged Eagle 331 cid bottom-end (actual displacement = 331.64 in^2)
• Trick Flow cam (51402000) with stock 1.7 Cobra rocker arms – intake/exhaust duration (at 0.050”) = 221/225, intake/exhaust lift = 0.530”/0.541”
• Heavily ported/polished stock Cobra GT-40 heads with recent valve job
• Ceramic coated BBK Equal Length Shorty Headers
• Off-road H-pipe
• BBK fender well-feed cold air intake
• BBK fuel pressure regular/gauge set to ~39 psi without vacuum
• 190 lph Holly fuel pump
• MSD Pro-Billet distributor
• MSD Blaster TFI coil
• Stock Cobra upper/lower intake manifold
• Stock Cobra 24lb Ford fuel injectors
• Stock Cobra mass-air meter (24lb calibration)
• Newly replaced IAC, TPS, and coolant temperature sensor
• Stock 95 Cobra computer calibration: J4J1
• fresh engine: <3,000 miles
So far the modifications I made to the scalars in Tweecer are:
• adjust engine displacement to 331.65 in^2
• increased idle RPM in neutral to 800 RPM
• increased idle RPM in gear to 800 RPM
• increased minimum tip-in retard to 15° (for diveability)
After making these changes and uploading them to the Tweecer module the car seemed to run a "little better" but the idle still stinks; it was just as bad before the Tweecer. When at idle usually one of two things happens:
1. after the initial high rpm at startup the idle settles down to ~900-1,000 RPM (slightly above what is called for) for about 10 seconds then belches out about 3 good idle surges and dies (unless you give it gas during the surges - which is what I have to do at redlights to keep the car running...not good for keeping a low redlight profile)
2. or, more even more strange - the car will go into some bizarre mode where the spark advance is absolutely pegged at 30° (observed using Tweecer RT) and the car idles at ~2,000 RPM. It will stay in this high RPM/spark advance until the car is turned off.
I guess my first question is - how does one properly tune for idle in my situation (increased displacement, hairy cam, ported/polished heads...)? I've looked all over the web (surely missing a good reference) but there appears to be no: step 1...xyz, step 2...xyz, after that xyz... for idle tuning.
Any and all guidance/suggestions are welcome - please pour it on!
Thanks,
David
To get the engine mods out of the way and let you know what we're dealing with, they are as follows:
• Forged Eagle 331 cid bottom-end (actual displacement = 331.64 in^2)
• Trick Flow cam (51402000) with stock 1.7 Cobra rocker arms – intake/exhaust duration (at 0.050”) = 221/225, intake/exhaust lift = 0.530”/0.541”
• Heavily ported/polished stock Cobra GT-40 heads with recent valve job
• Ceramic coated BBK Equal Length Shorty Headers
• Off-road H-pipe
• BBK fender well-feed cold air intake
• BBK fuel pressure regular/gauge set to ~39 psi without vacuum
• 190 lph Holly fuel pump
• MSD Pro-Billet distributor
• MSD Blaster TFI coil
• Stock Cobra upper/lower intake manifold
• Stock Cobra 24lb Ford fuel injectors
• Stock Cobra mass-air meter (24lb calibration)
• Newly replaced IAC, TPS, and coolant temperature sensor
• Stock 95 Cobra computer calibration: J4J1
• fresh engine: <3,000 miles
So far the modifications I made to the scalars in Tweecer are:
• adjust engine displacement to 331.65 in^2
• increased idle RPM in neutral to 800 RPM
• increased idle RPM in gear to 800 RPM
• increased minimum tip-in retard to 15° (for diveability)
After making these changes and uploading them to the Tweecer module the car seemed to run a "little better" but the idle still stinks; it was just as bad before the Tweecer. When at idle usually one of two things happens:
1. after the initial high rpm at startup the idle settles down to ~900-1,000 RPM (slightly above what is called for) for about 10 seconds then belches out about 3 good idle surges and dies (unless you give it gas during the surges - which is what I have to do at redlights to keep the car running...not good for keeping a low redlight profile)
2. or, more even more strange - the car will go into some bizarre mode where the spark advance is absolutely pegged at 30° (observed using Tweecer RT) and the car idles at ~2,000 RPM. It will stay in this high RPM/spark advance until the car is turned off.
I guess my first question is - how does one properly tune for idle in my situation (increased displacement, hairy cam, ported/polished heads...)? I've looked all over the web (surely missing a good reference) but there appears to be no: step 1...xyz, step 2...xyz, after that xyz... for idle tuning.
Any and all guidance/suggestions are welcome - please pour it on!
Thanks,
David