Spring Hopping!

[cygnusx1]

Well I just wanted to run through my current project. I successfully dropped an 83 Turbo motor/eccs into my 76Z last year with a SS 2.5" open exhaust and downpipe. It ran great BONE stock with 100K on the motor. I had tons of fun but I knew the 100K turbo was going to fizzle soon. Next I made a grainger type controller and boosted to 10psi. I had fun for about 2000 miles and then geriatric turbo started to hobble. "zcarsmakemyheadhurt" has hooked me up with a TO4B hybrid turbo and I picked up a nice new 17" x 8" x 3" Spearco. I am adding the adjustable BEGI FMU for boosting the Fuel pressure on boost. I subsequently purchased the Holly (Walbro 265) external fuel pump from Summit to help acheive the fuel pressure and flow that I may need. I am also going with a 240SX Throttle Body and a nice Mr. Gasket 16" electric fan which is very thin and should give clearance for the IC return pipe; again from Summit.

 

I am still assembling the machine and I plan to tune it conservatively at about 14psi boost peak. I think that the FMU and stock 83 fuel system will be able to keep me in the right A/F mixture range at least up until 14psi boost. I won't be racing the car officially. I am going to drive it to shows on nice weekends and run a few twisty roads around town.

 

I hope to see anywhere from 260-280rwhp and 300-315 rwft-lb when I get it on a dyno.

 

I reinforced the front diff mount by bolting a stainless strap to the upper part of the mount and wrapped it under the crossmember with a hard rubber strap sandwiched under it to act as an anti-noise cushion. CV's are in the future plan.

 

I will follow up as it progresses.....or blows up

 

Any further suggestions, comments, tips and tricks?

 

Dave

[Guest bastaad525]

the FMU is probably going to be overkill. For a long while I was convinced that I needed one of these. I've done a lot of looking and asking about the BEGI FMU and have come away with the impression that it's really only useful when you're dealing with a car/motor/efi system that was originally never boosted. Lots of people have great results with them using them on turboed civics or whatever, but even in those cases it's more considered as a 'bandaid fix' than a really good setup. Anyways, for an already turboed car, when you're using this FMU, it's going to provide enrichment on boost all the time, but really, the stock turbo ECU provides plenty of fuel on it's own up to a point, which is usually right around where the stock AFM stops measuring the airflow. At 10psi this is about 5k rpm. Even at 14psi, the FMU is definately going to supply too much fuel at some point, whenever you're on boost but not at WOT/full boost, for instance. I have been told many times that they can also be a pain in the ass to tune well. There are others here who can explain it better, why the FMU isn't really the best choice... it was explained well enough to me to change my mind about getting one.

 

I now believe that the best way to get extra fuel from the stock ECU is to either go with bigger injectors, or with increased overall fuel pressure. Then tweaking the tension on the AFM spring to get rid of the richness at cruise and mid RPMs. This would still leave the top end richened and should be able to support 14psi or whatever. Lots of guys here have done this with great results... yet there are few if any guys I've seen running that FMU, and a couple that have tried it would advise against it.

 

If you have your mind set on the Bell FMU, at least consider (if you haven't already) getting the one with the onset of gain adjustment. Though I've heard this feature doesn't work so well, this would at least allow you to roughly adjust when (at what amount of boost) you want the FMU to start affecting your fuel mixture, as well as the usual adjustment for how much more fuel you want it to supply. I'd use that and try to adjust it to do nothing until maybe 7psi of boost was reached.

[Guest znow white]

ahhhh HA! caught you. I can specifically remembering you not going to go over stock limits but hey Iam proud of you it takes allot. It took you a year to finally realize it NEED MORE BOOST? ! Keep us updated with some pics I like your swap too it was clean.

my .02 bigger injectors and some tuning with the afm as well your gonna need aftermarket fuel rail if you get o rings.

[cygnusx1]

Yes I know its addictive, I turned up the boost in my WRX within 2 months of buying it new..and I'm conservative

 

bastaad525,

The FMU I got has onset adjustment. All it does is bleed the boost signal so that the diaphram to raise the fuel pressure acts more slowly. I understand that ideally the FUEL CURVE should be BOOST, AND RPM dependant. But I'm really going to try to use the FMU to keep from getting too lean under WOT and at Max boost. After reading your reply, I thought about that grainger valve I built for the wastegate actuator. If I put one of those in the boost sense line of the FMU, I can have the FMU sitting pretty doing nothing until a preset boost around 90% of my max boost setting at the wastegate. That should keep everything running on pure stock ECU parameters until Max boost. Larger injectors would be nice but I just cant see changing them just yet. I will look out for all the pitfalls of the FMU and will try to make it work. My argument, like yours, is that the stock Turbo EFI system is pretty much capable of handling intercooled, 10-13 psi based on the general consensus here. On that note, I would like to run on that edge but have that FMU "band-aid" up my sleeve to keep from leaning at the breaking point. I do not race and dont drive it much, so for the few occasions that I get next to a "Hawnda" at a light , I dont want to worry about going lean.

[Guest bastaad525]

I guarantee you, without either bigger injectors or more fuel pressure, the stock EFI most certainly will NOT supply enough fuel for 10-13psi, ESPECIALLY with the I/C (I/C = colder denser charge = more oxygen = more lean). With my non I/C'd turbo, bone stock EFI but with a high flow fuel pump, at 10psi (non I/C'd, way hot and less dense, way less oxygen) I ran at 13:1 air/fuel ratio above 5000rpm... not safe. Tyson280zxt, who I know posts over at Zcar.com, ran a bone stock EFI on his ZXT with an I/C at 8psi, and was also way lean above about 5000rpm. 13psi of I/C'd air is a LOT of oxygen and once the air flow meter maxes out (somewhere between 4000-5000rpm at WOT) the computer goes to it's default fuel mixture which expects to see no more than 7-9psi (the limit at which the stock pop off valve would vent) of nonintercooled air... way less fuel than necessary to keep a safe mixture for way more oxygen that you'll be stuffing in there. I'm guessing that your argument is based on the calculation that the stock injectors can handle around 250hp, which is achieved at around 13psi of boost... and that IS correct... it's not the fault of the injectors that the EFI can't support that much boost, it's the fault of the factory fuel curve and the inability of the AFM to measure that much airflow. That's why even an upgrade to the Z31 setup with the stock injectors can easily support that boost... it has no cap on it's airflow capability like the AFM based EFI does. Of course, this whole issue is moot since you're going to be using the FMU anyways. Very good idea to use the grainger valve to regulate just when the FMU starts working.

[cygnusx1]

It looks good on paper! I will let you know how it works out. If I get it running nicely I will seek out a Dyno to get some facts and figures on the fuel curve/rpm/hp/torq. If I dont get it running nicely I will seek out hard engine parts to replace the busted ones Stay tuned. I still have a bit of assembly and fabrication to do. Good thread.

 

Lean is good for beef!