Boost gauge/FMU problems on KB blower

[stangGT95]

Went on test drive after install and it was like the gauge/FMU were seeing very little boost. I hooked a compressor to gauge and it read 16#'s so it's wired right. Also I applied vacuum to by-pass valve, & it opened. Is that how it is supposed to work? Both are on the boost side of manifold. Any ideas on what is wrong. Thanks.

[84gt347]

what series blower is it? Is there any chance the sending unit for the guage is out. ( asuming it is an electric guage)

[stangGT95]

I forgot to change crank pulley (underdrive). I'm hoping that was the problem. But had also found a small air leak at back of engine bay so need to find and fix before next test drive. It's a Kenne Bell 1.5 w/ flowzilla intake and 6#'s of boost.

[84gt347]

sounds like your on your way. those air leaks will kill you, as will that underdrive pulley

[stangGT95]

Is there another way to look for leaks besides spraying carb cleaner and waiting for idle to lunge up?

[84gt347]

only time will teach you what to look for. Hard surging idle and a propencity to die have been strong indicators. A real rich condition tells me a lot. I take lots of tylenol (sp)

[stangGT95]

Got it to read boost and increased FP. Just trying to figure if I should go to a 10:1 diaphram on FMU. With the 12:1 I'm getting a reading of over 1 volt from both O2 sensors. Any thoughts.

[stangGT95]

What should the FP reading be w/ 12:1 disk and 5#'s registering on gauge? (It has the stock FP regulator)

[84gt347]

(lincoln mk7 has the kenne bell) i don't use an fmu on this car, i have 42# injectors and a 255 pump and the kb chip, but , 12 psi of fuel pressure per lb of boost with 5 lbs of boost is 60 lbs increase. With no vacuum to the fpr, the factory reg should give you about 36 or 37 lbs of fuel pressure, so add 60 to that and 96 or 97 lbs is what i get. I have an fmu on my vert with a vortech and 42 lb injectors. I also have an adjustable fpr. I set the fpr at 40 lbs with no vacuum, and under full boost (15lbs) I see total 75lbs of fuel pressure. I would think if it takes 100lbs of fuel pressure to run the set up , Your injectors are too small. What size are they? I think the system would be more efficient at a lower fuel pressure than 100. Maby in the 75 range. Not too sure on that though. Maby 100 is fine.

[stangGT95]

I was getting a reading of 75 psi (and had heard that it was your disk/boost ratio plus half of base FP) which would be about right for my reading. Anyway my O2 sensors were reading over 1 volt so it was real rich. Plus I can see black around my grd effects near the tailpipes. Know it's best to be on the safe side but I also don't want to have to change fouled plugs. Learning as I go.

[84gt347]

Ill take rich over lean anytime. Hang in there

[stangGT95]

I know that's the way to go. I e-mailed KB tech on Friday to see what they think (and how to wire their boost-a-pump). Thanks for the help.

[84gt347]

yea, no problem, let me know how it runs. I like kb cars

[stangGT95]

KB recommended not to do the 10:1. Has anyone tried using an adjustable FMU? I was thinking of just tuning it to somewhere between 12:1 and 10:1 if that's even possible. 84gt347 the car feels fairly strong. Just kinda curious why with the 6# pulley it reads 5# boost. Possibly from the stock MAF I have on it now?

[84gt347]

Usually good heads and exhaust will cause a drop inboost from what kb says the pulley will produce. I have always been off a pound or two.

[stangGT95]

That makes sense. I think I'll try putting my 80mm MAF on to see how much of a restriction the stock MAF is. I almost have the boost-a-pump installed. But I'll not wire into fuel pump for now since my fuel pressure is right where it should be with the boost I'm running.

[84gt347]

My linc has an 80mm, i like it . i put it on from the start though, so i dont have a before and after senario.

[stangGT95]

Test drove after installing the 80mm. Boost went from 5.3 to 5 even. That sounds right to me, since there's less restriction. But a dyno book showed a stock motor w/ KB 1.5 and 6# boost went up 7#. Is that from them using the standard intake?

[84gt347]

i would have expected an increase in boost, since you have a bigger hole to draw through?

[stangsrule]

Do yourself a favor and get rid of that FMU as soon as possible. They are a bandaid and though they will get you going they make it hard to do do any real tuning. There are many options out there ranging from mail order chips (bottom of my reccomendation list) to on the dyno burned chips (near the top of the list) to full on programmers that let you tune and tweak everything yourself so as you make changes to your car's setup you can also change your computer's tune to match it. I have the TwEECer RT but there are many others out there with more being developed all the time. With the RT I can data log and also have a wideband AFR unit so I can see my AFR live and record it on my laptop. I would also recomend looking into a water/alky injection system, especially if you start to turn up the boost. I was having to mix race with a tank of 92 to keep mine from detonating with 7#'s of boost before, now with my SMS alky injection system I am running 14#'s on straight 92.