theshadow

I've just got a CBRD BBK turbo strapped to my car along with some 680cc injectors (also have HKS 272 cams, build head, FMIC, Walbro etc. etc.).

My tuner recommended upgrading to an ajustable aftermarket fuel pressure regulator and fuel rail as well.

Long story short - some issues fitting the fuel pressure regulator with the fuel rail, also not possible to fit my fuel pressure sensor to the FPR so I'm left with the stock fuel pressure regulator until we can find a bung to fit my gauge sensor and reinstall teh adjustable fuel pressure regulator in a few weeks but I still want to tune and run the car in the meantime (can always fine tune/retune later).

A quick search on EvoM here didn't turn up much about fuel presure regulators at all - I even came across one thread by David Burschur stating that he runs the bad bish in the 9s with the stock FPR and upgraded injectors. My tuner is highly in favour of having a FPR on the car so I'm kindof scratching my head right now...just looking for feedback.

Question is - do I really NEED an ajustable aftermarket fuel pressure regulator or not (and Im being fed a lot of BS)? Will the stock FPR work just fine with biger injectors? When do you NEED to upgrade to an ajustable FPR and what are the benefits of an adustable FPR?

More to the point - is the adjustable fuel pressure regulator *necessary* for my CBRD BBK/680cc/HKS 272/Walbro etc. setup or will I be just fine with the stock FPR?

Any help much appreciated - I'm just after peace of mind (and hopefully a successful tune tomorrow!!!) thanks!

gsrboi80

iTrader: (38)

PT61mm (AKA 35R), 880cc, BC272's, 4 year old single Walbro.

Stock Fuel rail and regulator

griffeyr

iTrader: (24)

you don't need it right now

1slowevo

iTrader: (96)

with your mods you are fine. no need for the adj fpr

theshadow

Thanks guys...keep the feedback coming!

CBRD

iTrader: (60)

we never really add them ryan.... we have made 500whp on pump on our mustang dyno with stock rail and regulator..

ok... so it was 499.7 but whose counting

cb

Mellon Racing

iTrader: (38)

600whp and twin fuel pumps + 1000cc injectors = stock FPR and rails here

Broxma

iTrader: (14)

You should only need it if the injectors aren't sized properly for your setup and you need to bump the fuel pressure to keep from running lean. Increasing fuel pressure isn't the best way to go about it though as the increase is not linear. Increasing IDC is linear, 1% in IDC is 1% more fuel.

For your 680's with a BSFC of .6 and a max IDC of 85% I get a max HP of 366. If the injectors can run at 95% IDC then it goes up to 410.

At 50 PSI FP your injectors will act like 730's roughly and at .6 BSFC/85% IDC I get 393 hp or 440 at 95% IDC.

So as you see the difference in bumping your base fuel pressure 7 psi only nets you 27hp overhead at 85%, while increasing IDC 10% nets you 44.

I don't know the ID of the factory fuel rail but since several people have chimed up already, I assume it can provide more fuel than your current injectors would ever need.

Size your injectors properly and you shouldn't need any FPR.

/brox

David Buschur

iTrader: (53)

The answer is...............

The stock fuel rail is good for about 700 whp on our dyno and then it needs upgraded. So you are good to go on that part for a long time.

The regulator will depend on what you want to spend your money on. Most injectors are rated for their flow at 43-45 psi of pressure. The EVO only has about 38 psi of rail pressure.

So, if you are running the stock regulator and you have a set of injectors maxed out (no matter what size injector you are running) if you add an adjustable regulator to the equation you will end up no longer needing to upgrade your injectors.

We do make a bolt on regulator that requires only unbolting your stock regulator and replacing it with the new adjustable regulator. The only thing you will need to do is have a gauge to set the base pressure. We can supply that too.

Mellon Racing

iTrader: (38)

I hope to have the need for that AFPR some day

theshadow

I hear what all you guys are saying and obviously there's quite alot of experience speaking here (wow and thanks by the way!) but I was out tuning my car today (with the 680s) and the guy tuning it said it was running out of fuel at the top end of the rev range and that adding a *rising rate* adjustable fuel pressure regulator (and possibly bigger injectors) would help since my fuel pressure seems to drop off at the top top end.

I wish I had more useful info than that - I'll really have to pull some datalogs off the car and have a look though through things so I can offer more useful feedback, like what kind of IDCs I'm running etc. etc.

Anyhow, does a 'rising rate' fuel pressure regulator make sense to anyone? I think I forgot to mention the 'rising rate' part in the original post.

Car is so-so tuned at the moment - still needs the fueling issue to be sorted and some heat range 9 plugs to be installed so might take my guy up on his suggestion and try the adjustable rising pressure fuel pressure regulator as the same time, might even try bigger injectors as well or might just try bigger injectors. Kind of confused actually.

I went with 680s because they were available even though CRBD themselves recommended 780s for the BBK turbo so possibly my bad there and might be able to fix things up with a simple injector swap (no big deal really). Wasn't sure how thirsty the new turbo would be so maybe injector size is the issue and not fuel regulation. Again, the datalogs will tell the story.

Sorry if I come off like a dumba$$ to still be asking quesitons after people like CRBD, Mellon and Buschur and everyone else etc. have already chimed in...can't help it, when it comes to tuning I AM actually somewhat dumba$$ed and basically just looking to max out my setup safely. Thanks for the feedback...it's nice (and interesting) to know that pretty much nobody in the US uses adjustable fuel pressure regulators except on pretty extreme cars....very interesting.

This CBRD BBK turbo seems to just looove timing and fuel by the way - and pulls like a mother at 1.9 bar. I think I underestimated it - it's way more than a little more than a stock 9 turbo...definitely need longer gears now. Yoikes!

Mellon Racing

iTrader: (38)

the stock fpr is a 1:1 rising rate meaning for every 1psi of boost the fuel pressure rise 1psi as well.

if you're IDC is too high make sure the AFR isn't too rich and if it's okay and you have a walbro 255lph pump already then it's likely time for bigger injectors and retuning.

theshadow

HHHemmmmm.....

Well I was hoping to be able to share some datalogs here to demostrate the problem. Unfortunately when we did datalog the car we a) didn't have the correct latency for the injectors and b) it doesn't really matter because the temporary tune I have on there is complete garbage!!! Starts throwing 6 counts of knock from 4000 rpms, down to 3-5 until 7k and then 10 counts of knock around 7k!!! Also noticed that the ECU is pulling fuel bigtime...from 255 gradually down to 251 at redline.

In short - need a retune BAD before I can even get down to analyzing fueling issues etc.

Can't even turn my boost down properly - using a Greddy EBC and no matter how much I turn down the gain and target boost I'm getting a huge spike to 1.8/1.9 before it settles and holds whatever target boost I want.

Soooo...lesson learned. Going back to my REAL tuner who lives in Singapore...far way form me in Dubai but the guy has done me right so far - previous tune was a zero knock 1.8 par tune that's never let me down on track. He's at least methodical, knows his stuff inside out and is a diehard 0 knock tuner - whereas the guy locally here has basically tuned me to blow my engine to bits it seems. Didn't even know how to set up my EBC (which he installed) and had to do it myself so he could "tune" me. Won't be going back there anyways. :P

Will eventually be sticking the rising rate pressure regulator on, just to get the most from my injetors while keeping atomization in check. It may fly in the face of what all you cuys are saying but I guess it's all about trusting the right tuner, eh?

If I was is the US I'd be happy to let someone else tune me of course...as flights form Singapore would be quite prohibitive

Thanks for the replies, will revisit this issue when I have my tune somewhat sorted out and can share some decent logs!

Chamama

You can also check out Mellon or the other reputable guys who tune through email. You will also learn a lot about your car in the process (I sure did!) .

I myself am running the FP WHITE and 26 psi boost till 6000rpm then falling to 23 by 7K. 0 knock. Using stock injectors, Walbro, seeing 101-103% IDC with 11.6 afr at redline. I know its borderline, but I am soon moving to BBK Full with 880CC injectors.

Good Luck!

theshadow

Yep I think you'll like the BBK Full with injectors for sure...it's a small turbo with a nice punch.

Tuning-wise, I'm gonna let my guy have his way with the car even if it takes a little time...he's THAT good. Would not hesitate to recommend Mellon as an alternative though