high rpm fall off

[paulbutvila]

Here's a question I hope someone out there can answer for me...At about 5000rpm my engine dies (falls off) power. If I drop a gear (hence rpm drops ) I gain power again up till about 5000 or so rpm and it does it again. My car ran very strong at 7000rpm before I sold and have since bought it back. There is no rev limiter on it, I have changed out the fuel pump, filters, plug wires, rebuilt destributor, new electronic ignition, the only thing I have not done is change the fuel reg. Got any ideas?

[Esprit Aviation]

Paul,

Check & verify, preferably in order:

Cam timing, ignition timing, fuel flow and fuel pressure (after the regulator), carb jets have not been changed by PO.

Then, let us know what you find. Post some pics of your car too!

Cheers, Lee

Edited March 16, 2007 by Esprit Aviation

[Tony K]

Hey Paul,

Not to be redundant, but I think you need at least 3.5 psi, if not 4.

And welcome to the best Esprit forum on the web!

- T

[paulbutvila]

Here is a shot of my recovered seats... I will add some more once the car has been painted

[dodgy]

Hmmmm, wrong thead i think

[tbeggan]

I had a high-rpm stumble a few years ago, it turned out to be a defective rotor inside the distributor cap. It had come loose and was wiggling around. It sounds as though your car may be acting differently though...... over 4,500 rpm, my engine would lose power and skip. It felt like it was misfiring and the car would shudder and shake a bit.

Do you just lose power gracefully? Or is there any shaking and shuddering involved? If it's a jittery experience, you may have a bad rotor/cap issue. If it's smooth, it's more likely to be a fuel pressure problem. Immediately, I'd check the fuel filter. Let us know.

Tom Beggan

87 HCi

New Hampshire - USA

Just re-read your post and saw you've replaced the fuel filter already. You may want to check the fuel line to look for crimps. It "could" also be dirty/clogged carb jets, so you might try some carb cleaner like SeaFoam, etc..

PS: Please post some pictures, I've never seen a G-car with a wing before, I'd like to see how it looks.

Edited March 17, 2007 by tbeggan

[paulbutvila]

I have checked everything...my power loss is immediate at 5000 to 5500 rpm. As i said once I drop a gear and drop rpm my power is back with no lag at all.

My rear wing is actually of a stevens car. Which is also a GM Fiero part you need to change the mtg brackets to get it at the right angle for the car. which I have the molds for.

[tbeggan]

I have checked everything...my power loss is immediate at 5000 to 5500 rpm. As i said once I drop a gear and drop rpm my power is back with no lag at all.

My rear wing is actually of a stevens car. Which is also a GM Fiero part you need to change the mtg brackets to get it at the right angle for the car. which I have the molds for.

Have you replaced the coil? It could be starting to weaken, and unable to produce enough spark at the higher RPM range.

[paulbutvila]

My mechanic replaced the coil. Could it be we need a diff. one? How do you know which one to use.

[dglotusltd]

Hey Paul welcome to the forum.

Been underground a bit due to work but I always check out this forum. The Yahoo forums don't seem to do it for me any more.

Here is an idea. Does your can have the rotor with the built in rev limiter. Its huge compared to the standard rotor and is design to interrrupt ignition between 7000 and 7200 RPM. Its mechanical so its not a precision instrument. Given its mechanical nature, I'd try a non-limiting rotor and see if you can get past the brick wall at 5000rpm. Of course if you have a standard rotor....then never mind.

I'll have to check but i think the coil (another suspect) is a 3 ohm 12 volt unit. My car actually died several times on the PO during my test drives. Massive loss of power. She would glide to a stop then start right up. I replaced it as soon as I got it with a Petronic expoy coil.

On the fuel side, the tank are notorious for rusting out. My right tank was so bad even the crossflow fitting was clogged. The filter was filled with rust particles and almost clogged the screens and needles in the carbs. Of course that would not be as sudden as your dropoff. My pressure regulator is set to 3.5 as Tony K mentioned.

DomG

[paulbutvila]

Hey Dom, nice to see you here. Your right, the other forum kinda sucks, nobody is posting much. Anyway, I have electronic gnition so no rotor. Its not my tanks as I would have a problem all the time. My problem is very predictable. Perhaps the wrong coil is on there. If it were a fuel problem I think that there may be a bit of a lag due to the float bowls needing to be filled again. My power is inatant as I drop rpms

[WayneB]

Wally, have you checked the accelerator linkage is opening the butterflys on the carbs all the way?

Maybe the cable, linkage, pedal , carpet has been altered ?

[Esprit Aviation]

Wally,

Even w/ electronic ignition, you must be careful to match the coil resistance to that particular system. otherwise w/ too high of a resistance,you will have a weaker spark, or too low, you will overstress the output transister in the ignition module. Many times a really 'powerful coil will be chosen, then the ignition transistor burns out from switching too much current.

I tend to doubt it is your problem though.

Lee

[paulbutvila]

Wayne, I did check the linkage and it seemed fine. The coil idea has me interested though...

[dglotusltd]

Paul,

My rotor comment was based on having used a Pertronix unit in my 74 Elite. That unit only replaced the points and still used the rotor arm to flow the high voltage to the plug wires.

You have an electronic setup that bypasses the dizzy? Else, something creates the high voltage path. What system are you using?

DomG

[paulbutvila]

Dom, I am using the Crane Cams Fireball XR700. My mechanic originally installed the ballast resistor that is recommended for use with this unit and then decided to dissconnect it as he felt it may be causing the problem but it didn't change anything so we left it unconnected.

[Esprit Aviation]

Wally,

Even w/ electronic ignition, you must be careful to match the coil resistance to that particular system. otherwise w/ too high of a resistance,you will have a weaker spark, or too low, you will overstress the output transister in the ignition module. Many times a really 'powerful coil will be chosen, then the ignition transistor burns out from switching too much current.

I tend to doubt it is your problem though.

Lee

If your system requires the ballast, then by all means it should be used. As per my last reply, now your resistance has been lowered w/ the removal of the ballast resistor. This causes the output tansistor to switch a much higher current than what it was originally designed for. It is relatively easy to verify the resistance of the coil primary circuit, then calculate the current draw based on the change from ballast, to no ballast.

CURRENT(I) = VOLTAGE(V) divided by RESISTANCE

Edited March 20, 2007 by Esprit Aviation

[paulbutvila]

Lee, The electromotive HPV-1 does sound like the answer. My Crane unit was installed only a few months ago, replacing it is a bit extreme $$ wise unless of course it is fried. Perhaps just running the propper ballast will help. Regarding the electromotive unit...Will it be fine on a non turbo car?Mine is a 77 esprit. Also can you remember what you paid for the unit? and how difficult was it to install?

Paul

[Esprit Aviation]

Paul,

I am concerned about the Crane unit since it is possible that the switching transistor may have been weakened as a result of running w/o the ballast.

The Electromotive will work equally well on a N/A engine! My friend in Canada has one on his 80 S2. He may be swapping it out for a complete fuel inj/ign system though. I had planned on aquiring his as a spare, perhaps to install in my Porsche.

The orig cost was approx 550.00USD three years ago. Dealers are typically less expensive than direct from Electromotive.

Install was relatively simple, but my friend had someone, custom make the sensor bracketry and machine the pulley to accept the trigger wheel. He also made a very elaborately machined aluminium box to accomodate the coil pack/module assembly.

All of this added once again, about half the cost of the unit, but you could install for much less.

Here are some pics:

http://i43.photobucket.com/albums/e399/esp.../picture424.jpg

http://i43.photobucket.com/albums/e399/esp.../picture405.jpg

http://i43.photobucket.com/albums/e399/esp.../picture404.jpg

http://i43.photobucket.com/albums/e399/esp.../picture383.jpg

http://i43.photobucket.com/albums/e399/esp.../picture350.jpg

Hope this is helpful. I will have to take a pic of the fancy box for posting.

Cheers, Lee

Edited March 22, 2007 by Esprit Aviation

[paulbutvila]

Thanks Lee. Where in Candad is your buddy? I will have my mechanic friend check out the unit before I change it out. He suspects that the coil may be no good so we will try that first.

[Esprit Aviation]

My friend w/ the S2 is in Ottawa.

Certainly worth a try to see if there is any change. You'll @ least rule it out as a potential problem.

Lee