Ford Focus Forum banner
Cancel
Create thread New Garage Forums

Fuel for 300whp..?

Jump to Latest
1 - 20 of 30 Posts
Z

ZXTOO

· Registered
Joined
·
317 Posts
Discussion starter · #1 ·
I have a ZX2 and right now the fuel system consists of an SVT pump and 42lb injectors. At 16psi I made 302whp. The fuel pressure was dropping off a bit in the high rpms so we had to dump fuel in to keep the a/f right.
I'd like to keep it at the current power level (or maybe another 20whp) but I want it to be safe. I want to get 60lb injectors but will that be enough? Will I have to get a BAP too? I'm trying to put an end to modding this car so the less I buy the better.
 
#2 ·
Does your ECU see the fuel rail pressure drop and compensate by lengthening injector pulse width or were you manually adjusting the fuel tuning?

42 lb injectors can flow enough to support your power goals. I really don't see a reason to swap them for 60 pounders. All that will do is lower your required pulse width and raise the inaccuracy of low RPM fueling slightly. Your problem isn't pulse width though it's pressure.

The BAP is very easy install and it has a pretty good track record. I would try the BAP first then worry about injectors second. Even with 60 lb injectors, tuning pulse width while having unreliable rail pressure is sorta putting the cart before the horse.
 
#3 ·
You know at 16psi of boost you should see 56psi of fuel pressure....

As a general rule of thumb its 1:1 on the boost/added fuel ratio
 
Save
Reply Quote Like Like
Discussion starter · #4 ·
DigitalGT said:
Does your ECU see the fuel rail pressure drop and compensate by lengthening injector pulse width
Click to expand...
Yes. At least I think so, its been a little while since I got tuned and I don't have any of the datalogs. The max hp for 42lb'ers was is supposed to be 305 so I figured I was close to maxing them out.
 
Discussion starter · #5 ·
OrangeSVT03 said:
You know at 16psi of boost you should see 56psi of fuel pressure....

As a general rule of thumb its 1:1 on the boost/added fuel ratio
Click to expand...
So in other words, I need a BAP. I thought the SVT pump was ok for a good amount of hp. Ugh, more money into the pit, lol
 
#6 ·
On my buddies SVT we datalogged the fuel pressure drop across the injectors, the SVT pump kept up great until 4300 rpm the it all went down hill until redline..... and thats was running around 12psi.

Here are a comparison of with and without the BAP....... Fuel pressure is the Yellow line

BAP OFF

Image





BAP ON

Image
 
Save
Reply Quote Like Like
Discussion starter · #7 ·
Ok so I guess that answers my question. The bigger injectors may fix the problem but they're being over worked due to insufficient fuel pressure.
So I guess my next question is will the BAP and 42lbs support 320ish whp or will I need a BAP AND 60 lbs?
 
#9 ·
I would go with a minimum of 50's... but you're problely better with the 60's

In the above datalogs the factory voltage limit is what caused the fuel pressure to drop off, at 4300rpm the fuel pump was at 100% of the factory duty cycle with the BAP you can go WAY beyond that.

Kenne Bell has been doing that to Mustangs for years without any issues and I dont see any reason that you cant do it to our pumps. I've been running my BAP for about 2 years and with 20psi @ 7000rpms I can still maintain 62psi of fuel pressure.
 
Save
Reply Quote Like Like
#10 ·
I've heard that 60s may be big enough to compensate for the difference in lack of fuel pressure by dumping more fuel, plus the duty cycle for that would be way lower. If you are going for 325whp like it sounds like you are, you are overworking the 42's--I believe at 85-90% duty cycle (recommended) that you max out at 318whp. I'd go with the 60s.
 
Save
Reply Quote Like Like
Discussion starter · #11 ·
polarisman14 said:
I've heard that 60s may be big enough to compensate for the difference in lack of fuel pressure by dumping more fuel, plus the duty cycle for that would be way lower. If you are going for 325whp like it sounds like you are, you are overworking the 42's--I believe at 85-90% duty cycle (recommended) that you max out at 318whp. I'd go with the 60s.
Click to expand...
I'd like to be able to get away with just the injectors if I could. I wanted to stop putting money into my car but injectors, BAP, and a MAF.ia + more dyno time is gonna add up. Has anyone used 60lbs without a BAP?
 
#13 ·
Did you even LOOK at the datalogs I posted... that was with 50's.

Just do it right and be done with it before you end up going lean and toasting a piston or two.
 
Save
Reply Quote Like Like
#14 ·
ZXTOO said:
I'd like to be able to get away with just the injectors if I could. I wanted to stop putting money into my car but injectors, BAP, and a MAF.ia + more dyno time is gonna add up. Has anyone used 60lbs without a BAP?
Click to expand...


yeap i had 60's with out a BAP u will need one or a return setup if u plan to go over 300, my FP was still dropping with the 60's
 
Save
Reply Quote Like Like
#15 ·
The safe way would be the 60lb injectors and boost-a-pump. Like orangesvt03 said it would be better to do it right than toast and engine. He noted atleat 50lb injectors, but 60lb injectors can be found for a lower price.
 
#17 ·
I know its a real pain to keep dumping money into a car... but look at it this way...

$400 now or a rebuild later.
 
Save
Reply Quote Like Like
#19 ·
siemens/deka makes good ones that are relatively cheap, 200 bucks or less for a set. They are good quality and I haven't heard of anyone having major issues with them. RC makes some 60s or 72s but they are 400-500 for the set IIRC.
 
Save
Reply Quote Like Like
1 - 20 of 30 Posts
About this Discussion
29 Replies
13 Participants
Last post:
polarisman14
Ford Focus Forum
posts
3.6M
members
67K
Since
1989
Forum community dedicated to Ford Focus owners and enthusiasts. Come join the discussion about RS/ST performance, modifications, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
TEAM Pit Stop Ford SVT Focus Headquarters Forced Induction & Nitrous MK I Tech New Member Introductions