3800 RPM Hesitation, Fuel Pulsation, FPDs.. random brain droppings
 

Ya know.... I've been thinking about the 3.8K hesitation that our cars are known for....

The main fix seems to be the ECU solder joint fix....... but i didn't bother doing that because I knew I was going to haltech the car..

Well.. I'm beginning to think that the ECU may not be the culprit, at least not all the time..

Like two years ago... I put a haltech in my car..... Ya know what.... I had 3.8K hesitation that showed up as a lean spot on the datalog at 3.7-4K and it was WAY worse than it was before..... I could do nothing about it.. NOTHING..

Until I put a marren pulsation damper on the car.. I had eliminated the stock FPD when I switched to Braided Fuel Lines... Well... that SORTA fixed the problem.. the lean spot woud STILL show up from time to time, depending on the load the car was at when it reached 3.8K...

SO...... I switched to marren 750 primaries..... the lean spot MOVED..... it MOVED to 3.5K.... consistantly...

SO...... I changed the location of the FPD.. i HAD it mounted off the back of the secondary rail, I moved to the front end of the primary rail (talk about a BITCH running THAT plumbing in the cramped space of a TII).

GONE..... Lean spot and hesitation TOTALLY GONE.....

Sooooo lets think about this.... had 3.8K hesitation... Switched to a haltech, thus eliminating stock ecu, eliminated stock FPD,, 3.8 K hesitation got WORSE... Put FPD on back of secondary rail... hesitation got better, but still there, switched injectors from stock to 750's... Hesitation MOVED in the RPM range.. (Hmmm hesitation just MIGHT be linked to the injectors)... Relocated Marren FPD to end of primary rail...... Gone.......

So.... If you do the ECU re-wire and the hesitation is still there.. maybe old Decay is on to something here..... Try a new PD or a Marren PD off the end of the primary rail....

I've ALSO noted that cars with Braided Stainless Steel Lines are more prone to hesitation from lean sports... why?? I THINK the stock rubber lines act as a pulsation damper themselves.... If you feel a stock line while the injectors are firing... you can FEEL the injectors pulsint in them, HARD..... Not so with a braided line.. you can feel the vibration, but not the thum you get from a rubber line... this tells me that the rubber line is absorbing some of the pulsation, the stainless is not!!

If the ECU re-solder works.. GREAT... believe me, its MUCH less expensive and PITA than running an after market FPD.....

So - now that it's all sorted out, you can sell it & start on a 3rd gen. HA!

BTW - I finally got smart & wired your FCD in at the ECU.

Nah........ 1st gen!!!!! with a Supercharged, Injected, Ford 289 out of a 67 cougar (pre emissions motor), a Narrowed ford 9 Inch rear and a C4 with Transbrake and a Line lock on the fronts brakes to burn off the tires!!!!!!

Very interesting. I wonder why moving the FPD worked. hmmm think think think.

The 289 motors were :puke:

The reason you get that lean shot especially when you run larger injectors is that when the injectors piston fires open shut open shut they create harmonic bounces in the rail. These waves will cause the fuel to be interrupted and not reach the injectors. Suddenly you have lean shots and well stutter now too, if the problem is server enough a popped motor.

IMHO the only way to run a fuel setup is independent to each rail with a PD on each rail no exceptions or you will receive harmonic interference in each rail.

A batched fuel setup without a good PD is a sure fire way to blow the motor. I don’t consider the ones from SX and AM with built in PD's anywhere sufficient to handle the harmonics that out large injectors send like 1300cc and so on.

my car is doing this very thing.. thanks alot for the info guys!! :bigthumb: