93 Cobra hitting the wall at 5400RPM

[Fast]

OK,93 Cobra,pretty much stock except for these mods

Autolite 764 gapped at .030
Crane Hi-6S w/ TRC-2 (timing retard) set at about 2:1 timing:boost
Vortech SC-trim putting out about 9lbs of boost
36lb injectors witn NO fmu
75mm bullet pro-m
a9l computer
kirban fpr
255 high pressure walbro intank
timing set at 10 degrees
fuel pressure is at 40 with vacuum off


what could be causing this car to pull up to 5400 then just hits a wall...is this about all you can get out of a stock longblock cobra motor?

[mustan5069]

OK,93 Cobra,pretty much stock except for these mods

Autolite 764 gapped at .030
Crane Hi-6S w/ TRC-2 (timing retard) set at about 2:1 timing:boost
Vortech SC-trim putting out about 9lbs of boost
36lb injectors witn NO fmu
75mm bullet pro-m
a9l computer
kirban fpr
255 high pressure walbro intank
timing set at 10 degrees
fuel pressure is at 40 with vacuum off


what could be causing this car to pull up to 5400 then just hits a wall...is this about all you can get out of a stock longblock cobra motor?

bump your initial timing up to 15 or so and leave your boost retard same
sounds to me like your pulling out too much timing

[speedytang]

Example: 10psi
Timing Total 26 degrees - 2 degrees for each 1psi = -20 degrees leaving 6 degrees total timing. You should be at about 19 degrees at 10psi.
With Hyper Pistons I would stay at the 19 degree area not more.

[Fast]

OK,so if the TRC2 box was set at 1:1 would thise still cause the same problem?

[Chuck]

Is it misfiring at all. You could also try to close up your spark plug gap.

I have heard Alternative Auto goes as small as .026

If it is blowing out the spark it will feel like you were hitting the rev limiter.

Also keep your ear open for detonation with the hypereutectic pistons, they wont take the detonation as good as forged.

[fanglemeister]

If the tune is on, you probably need new valve springs. They are 12 years old after all, and oem springs are basically shot as of the first time you rev your engine over 6k rpm.

edit: might try some NGK TR6 plugs. But my money's still on the weak springs, btdt. ;)

[RSNovi]

How high did it pull without the blower. If it pulled higher, then it is something with fuel or spark. Most likely spark.

I would focus on the cap, rotor, plug wires, and possibly try a colder plug. I am not familiar with GT40 heads, but I don't run anything hotter then an AR3924 on TFS TW heads. On my Real Street motor, I run about 4 to 5 heat ranges colder then stock.

[mustangcobra93]

hey guys, this is my car. I have switched the plugs from the 764's to TR6's and kept the gap at .030. I think timing was the issue. I turned the TRC-2 off and took it for a spin and it pulled pretty well up to 5800 rpms. Therefore, would it be better to leave the trc off and rund 10 degrees of timing or do like suggested and bump the base timing up and run the trc? If the latter is the way to go what should the base be set at and what whould the trc be set at?

[fanglemeister]

Here's the stock WOT timing curve for your Cobra, with initial set to 10 degrees:

WOT_ADVANCE_VS_RPM
( 16383.8, 25 ) ( 5000, 25 ) ( 3500, 22 )
( 2600, 22.5 ) ( 2150, 21.5 ) ( 1800, 18.5 )
( 1000, 8 ) ( 0, 8 ) ( 0, 8 )

I'd say a nice curve might be initial at 13-14, TRC set for 1:1, this would give you WOT total timing of 18-19 at 10psi. Make sure you are pulling the TRC boost signal directly from the intake manifold, and not from a remote spot like the vac tree, this will give you a false low reading.

I would also verify your fuel mixture with a wideband O2 sensor, the factory WOT a/f is dependent on several variables, might be 11.5:1 one day and 12.15:1 the next, which is a bit on the lean side for 10 psi on hyper pistons.

[mustangcobra93]

I have the A9L in stead of the cobra computer so does that change anything?

[fanglemeister]

Oops, my fault, didn't spot the A9L in your mods list! :-)

The WOT timing will be only slightly different, 26 instead of 25, and the WOT a/f will be a little more steady, should peg @ 11.8:1 most of the time, but still might vary a bit, might go up into the low 12s, depending on variables like intake air temp. Speaking of which, if you go with some sort of aftermarket eec tuning, you can alter the ACT timing retard curve to handle boost timing retard internally, lots of guys with eec-tuners are doing this, since there's no MAP sensor for the A9L etc to sense boost.