Sorry I've been busy with work and haven't had time to post the results from the dyno tune.

Long story short. We didn't get a chance to tune the car, all we did was a few short pulls to 5400rpm or so Because we ran out of injectors.

Currently, I am running the Motron 60# injectors. I was told these injectors will support close to 900rwhp. However, this didn't seem to be true as we started to run out of fuel at around 4500rpm @ around 10.5psi of boost.

The numbers are on a dyno dynamics load bearing dyno, which is similar to the mustang dyno and typically reads 15-18% lower in numbers when compared to a dynojet dyno.

The car made 478rwhp and 510rwtq @ 4700rpm when it ran out of fuel.
I played with the VE tables on the DFI until the numbers were maxed out and the car was still extremely lean as soon as we hit 10psi of boost. At that point there was nothing we could do but change injectors so I pulled the car off the dyno.

Here is what got me confused?
why did I run out of injectors at this hp level. With the same injectors on a S trim I made close to 580rwhp @ 6200rpm on a dynojet and the AF ratio was just fine at 11.8:1? If you add 18% to 475 it gives you 560rwhp and my AF is no where near what is was before? The only thing different is the head unit.

Why did the boost level drop off after 4500rpm? This is a YSI trim unit and should be making much more boost as the RPM rises. There were no signs of belt slip or leaks anywhere? I didn't drive the car, and the two guys operating the dyno did a very good job on keeping their eyes glued to the AF meter. Basically, once the AFR got over 12.5 to 1, they let off. They did do one 3/4 pull to 5800rpm but the boost never went past 10.5psi. Infact, it dropped!?

I tried to look up the injector duty cycle on the DFI and instead of %, all it showed was a single digit number. I didn't get a chance to datalog it but the numbers ranged from 1.5 to 2.8? What does that mean?

I think before I start to worry about boost levels and hp I need to figure out why I am running out of injectors at this power level.

In the C5 and C6 FI section, I see plenty of guys running the same motron 60s and they are getting over 700rwhp without issues?

Anyone with any knowledge of FI, DFI or injectors please chime in and share your thoughts! Mods are in signature, the only changes are 60lb injectors, and YSI blower.

Here are some pics.
This one shows the HP and TQ

This one shows PSI and AFR

Pre-dyno pic

another one from the side

Here is a pic of the shop owner's 1400rwhp supra. 91mm single turbo with a TH-400.

One more from the back

 

I see no mention of fuel "system" anywhere? Or fuel pressure readings when boost/power drops, and a/f goes lean.

I've personally made 502rwhp/543rwtq on a (18psi) YS trimmed car (not a Vette, but it's irrelevant in this discussion). It made more soon after as the car was tweaked on and went from 10.40's to 10.20's, but when it was dynoed, that's what I made. That was with 42# Ford/Bosch injectors, BUT....

I also had Aeromotive A1000 pump, -10 feed from sumped tank to pump, -8 lines to 1/2" rails, -6 return. I only had issues with the same setup when my fuel system couldn't supply enough fuel to the injectors. Supposedly, it's a common issue if lines and/or pump(s) cannot maintain the VOLUME of fuel needed to feed the car's requirement.

In other words, you could have 150# injectors tuned for your car, but if the fuel volume isn't there, neither is the power, or the proper and safe a/f ratio.

FWIW, when my first Aeromotive pump did indeed start to die on me, the car was so lean that it did not make power, did not make more than 12psi of boost at wot, and also was so lean that it couldn't even blow a head gasket. I thought my tuning helper was nuts when he said that a car can be so lean that it simply won't make power. I went from my usual 10.20's, to 10.80's and lost 10mph! Never hurt the engine though. Swapped on new pump, 10.20's and 130mph+ was instantly back...as were safe a/f ratios.

 

Sorry, the fuel system is as follows.

Mallory 110FI external pump. This pump will support 1000+hp. 10AN feed line to pump, 8AN from pump forward to fuel rail, and 6AN return line. Just before the fuel rail there is an aeromotive fuel filter. The fuel rail and line on the miniram is untouched.

Fuel is at 45psi idle and rises to about 52psi under boost.

There is also a Kenne bell BAP. which we didn't use on the dyno because I felt the AFR was way off and shouldn't use another band aid tool to fix this problem. I probably could have gotten the AFR under control by cranking up the kenne bell BAP but what if the BAP fails one day under WOT?

 

Very nice ride!!! The number you see, and that you posted looks like injector on time in milliseconds. I hope its not, but thats what it looks like. Are you using ACCEL DFI? Let me know what you're running and I'll try to figure out how you need to configure your screen to capture the needed info. I've got all the software for most all the aftermarket DFI systems. I do so many different ones, its hard to memorize exactly what is what. But if you tell me what you're running, and how you've got it set up, I can go to my program and figure out what you need to do.
Also, you mentioned you maxed out the VE table. Did you adjust the A/F table any? What is your commanded A/F under boost? Are you running a 2 bar?

 

hmmm, you'd think that'd feed it. I was at 99% duty cycle (basically running them static) by 1000' during a WOT 1/4 mile run, but I only ran 45psi base fuel pressure too.

That looks like the same Aeromotive regulator that I used. Are you 100% sure fuel pressure was holding under boost? Just wondering where you are reading the FP at? I don't see anything right on the regulator.

My setup had also went from an S trim to a bigger YS (No YSI at that time), and only needed slight tweaking of injector fuel percentages. Unfortunately I didn't use a DFI (so I cannot offer anything on that), I had a piggyback programmable management system on that car.

BADASS looking setup you have there BTW!!!

 

I've seen the same thing. So lean, it wont even ping!! But your butt hole kinda puckers when you see the A/F shoot of the chart!!!

 

If the fuel pressures you listed are actually happening, you've got fuel system problems.

With 10 psi boost and 45 psi fuel pressure idling, with a 1:1 boost referenced fuel pressure regulator I'd be expecting to see 55 to 57 psi fuel pressure under boost.

Those Motrons are supposed to be able to support the power you're talking about in the 85 psi range.

 

the fuel pressure gauge is right there in your face. You can't miss read it.

I had my eyes on the gauge the entire run. THE FP never went past 54psi.

 

I don't have a FMU? is that what you are talking about?
The fuel pressure has and is always steady. 45 at idle and around 53 to 54psi at full boost. What do you think is wrong?

 

Thanks! Yeah I am running the accel dfi gen VII. I did set the target A:F ratio but we ran it in open loop mode so I don't think it has an affect. BTW: the target AF is set at 11.8 under boost at WOT.

Yes, two bar map and I thought with 11psi at 4500rpm I would definitely need a 3 bar map at 6500rpm. But the boost never gets over 11psi and it actually started to drop as rpm rose.

 

Paul, typically when I see boost dropping off as RPM increases, it is an indication of either belt slippage or perhaps the blower intake is restricted in someway.

 

Tom,

Thanks for the reply. I am 100% sure belt slip was NOT an issue.

I can't think of any restrictions in my intake setup???

 

ouch... that hurts... It sounds like you're one to one fuel pressure regulator was working. You should be seeing more boost and hp #'s. It's almost like things signed off early. What about spark plug blowout? You should be making much more than that even with belt slippage if you're seeing approx 10 lbs of boost. It sounds like slippage but let's see if I can come up with some other ideas...

FWIW, shopview got 17 lbs of boost out of his lt1, even with slippage. That was around 700 rwhp.

 

Make sure the BOV isn't leaking. You may want to remove it and build a block off plate just to try it. $5 of metal stock from home depot and a drill and you can eliminate that.

I would also remove all the intake plumbing up to the supercharger. Running it without an airfilter for a few miles of testing shouldn't hurt it.

You may want to bump up the fuel pressure as well. Are you running 45psi at idle? You need to set your base fuel puressure with the fuel pump running and the engine off, or the vaccume line disconnected and make sure it increases 1psi/psi of boost. A normal fuel pressure regulator will increase pressure at a 1:1 ratio, an FMU will increase it at a much larger ratio, 12:1 or so. Even our stock fuel pressure regulators act this way. But you can't set the base fuel pressure while the engine is idling because the idle vaccume in the engine effects the fuel pressure too.

 

Assuming a 1:1 FMU or regulator, I think you should be seeing much higher fuel pressure. Assuming you are pulling 18inches of vacuum at idle, you should see an extra 18/2 = 9 psi at 'zero' vacuum and than another 1 psi per lb of boost:

45 + 9 + 10 = 64 psi.

Have you changed the fuel filter recently?

 

Did you log fuel pressure?

60's will make tons of power. At your level you should have been able to get by with 42's.


As far as knock and being lean.... You have to have a relatively dense charge to knock. flame travel speed is a function of air fuel ratio.. when the mixture is lean the flame cannot travel quickly and you will not see knock. You will see higher combustion temperatures because the burn is so slow that less work goes into expansion (that shoots up quickly the first 45 degrees of crankcase revolution) and more of it goes into heat.

 

I see a bunch of good comments above.

A few that stand out as worth trying:
Fuel related:
1) the MRII fuel system is untouched.
If this is correct, then the L side injectors are getting fed with an ~-4AN line, as that is what the internal passages are sized, as well as the xfer port. This is an area that will need attention.
2) the fuel psi seems low under 11 psi boost.
I typically add 7 psi to the base for NA, then 1:1 above that. So in your example, you should have seen +16 psi, and you were seeing +9 psi. You have a fuel delivery issue. I think your line size is fine. I have had bad experiences with the Aeromotive pumps, but no experience with the Mallory, but the symptoms are similar to a failing pump. I would not tune with the BAP connected. Check your filter, especially if the suction side is running anything less than a 20um filter (btw, that filter is tiny).

I run a 5" Weldon 25um filter in front of a Weldon pump, -12AN feed to a 8" Aeromotive 5um filter that splits to 2 -8AN to the rails, 84 lb/hr Siemens injectors, -6AN twin returns to an Aeromotive 1:1 boost referenced regulator to a single -8AN return to the tank.

Boost levels:
1) 3/4 run to 5400 RPM
anything less than full throttle and the blow off valve will be bleeding some volume of air from the system.
2) remove the inlet to the blower
I had mentioned this early on, as it seems like a restriction in your combo. Have the dyno operator pull it just to verify once the fuel issues are addressed.
3) Once the fuel system is addressed, and the engine can be run at WOT, I am sure you will see much higher boost. FWIW, mine gains over 10 psi between 5000 and redline.

I hope this helps,
Aaron

 

Thanks for all the reply guys.

What could be causing the fuel pressure not to rise to the appropriate level? How can I diagnose for this problem?

 

Change or clean the fuel filter(s) before you do anything else. If the fuel psi issue continues, then you may have diagnosed the pump as an issue. What was the fuel psi at max boost with the old combo? (i.e. base 43 psi, 60 psi fuel psi at 10 psi boost)

Aaron

 

Aaron,

Do you think I have to change the fuel rail line on the MR?

I just found a tear in the silicone sleeve just off the discharge side of the blower.

Apparently, where the hood was cut it left a sharp edge and was cutting into the sleeve when the hood was closed. I will change the sleeve and see if this fixes the boost problem. If not, I will try to remove the intake plumbing upto the blower.

Thanks,

Paul