snkchrmr

I need some suggestions. took the car to get it tuned yesterday and it isn't making close to what it was prior forged short block. So here's the run down. Car is an 02 ws6 MN6 Lt's, slp LM2, blower cam 224/226 562/567 114, P1 procharger @ 7#. The car made 549/494 with 18*. Okay now I've added front mount IC and a forged SB, still stock cubes, meth and more boost. Car made 475/446 on 10#! WTF took the inlet hat off and car made 530/479 on 13.5# with 21*! Now the only issue I know for sure is the fuel pressure was dropping at 5k rpm. I'm still on the stock intank and a 255 inline pump with 60# injectors. The A/F was 12.0 across the board with a slight dip between 4k to 5K.

So does anyone have any suggestions on why the car isnt making power. Could it be because of the fuel pressure drop and its running on more meth? I don't post much so I don't know how to post pics but if somebody will post the dyno sheet I will email it to them.

Thanks any help is appreciated!

speedcrazy2

iTrader: (1)

those first numbers seem really high for 7lbs on a stock shortblock,most people I have seen make about 500 on 10lbs. of boost on stock motors



also the intercooler could be a big restriction if you went with an ebay unit or something cheap

and the fuel dropping at 5k leaves alot of power on the table also


you still have 1000-1500 rpm or more left so you will see alot of that power back in that range when you get the fuel supplied to it


these are just a few of my thoughts on the subject but I am no expert so you might see what some others say also

snkchrmr

I've seen a few people making in the low to mid 5's with 7# and cam, but thats not in question.

The front mount is an OBX. I had the procharger twins on there before. They are 2.5' piping and I have 3" now.

As far as the 1k or so rpm up top to make power, is it's not making any where close to the same power curve as before. Plus the car is a turtle now! lol.

Aster

iTrader: (9)

Did the compression change much on the new motor?
What thickness OBX intercooler did you get, 3" or 4"?
Also there is a big restriction in your filter setup, get a better inlet/filter.

Get the fuel straight, you are likely going through the available fuel much sooner than before which limits it.
Have you made sure the engine is sealing properly and not blowing by or losing compression?

BLOWNBLUEZ06

iTrader: (17)

Are you logging boost or did you simply look at the gauge once, so you know how much boost it's making? Reason for the question is i'm wondering if you have a boost leak. I would recommend a boost-leak test. Then start doing pressure drop tests across your system. If you have 16lbs at the inlet to the OBX intercooler and 12 after, then that is killing you. 1lb drop is reasonable across a good intercooler.

snkchrmr

The compression was suppose to stay at 10:1 or right at it. It has 4cc dished piston in it according to the builder. I'm starting to wonder if its not a low comp motor. lol

It's the 4" OBX. The car still was trapping the same mph when I switched to the front mount before ringland let go.

Yeah it makes 9# to 10# with the filter on the car and 475hp. With filter and hat off it seen 13# to 14# and made 530hp. Where as before on the stock short block it was seeing 7# and made 550? So yeah I don't know.

I have catch can with breather and breather on the oil fill. The catch can doesn't have a hint of oil. Also front and rear seals aren't leaking or any thing.

snkchrmr

I have the Autometer gauge with the peek boost recall on it. It works off of it's on map sensor.
Yeah the car is seeing boost it's just not making power.
I wish I could get the graphs up so everybody could see the difference from before on 7# stock sb vrs 10# and 13# on new sb.

XtremeDime

iTrader: (16)

Where is the boost guage sourcing its reading at? On the manifold?

snkchrmr

It's tied in at the vac line coming from the back of the intake that leads into the firewall at the pcm.

I'm starting to think they put the wrong pistons in the car and it's low compression! lol

rotary1307cc

iTrader: (5)

what is the cranking compression pressure?

snkchrmr

Idk going to do a compression test on it tomorrow and see where I'm at. I'll post up the results.

snkchrmr

Late crew bump

blue00ZZleeper

iTrader: (5)

Any more info?

snkchrmr

Not yet im am fixing to do a compression test in a few. Got to thinking though and I had the meth to start coming on at like 2# and wide open at 6#. Just wonder if having the meth coming on that early was killing power down low? Idk but ill post up the results from the compression test.

snkchrmr

Well all cylinders checked 100 cold. I didn't warm the car up just checked them cold cause I didn't feel like getting burnt. Lol I was just wanting to make sure they were all the same. Going to do the fuel system and try it again.

rotary1307cc

iTrader: (5)

100!?!

You absolutely sure you did it correctly? Throttle was wide open?

Aster

iTrader: (9)

If your compression is only 100 something is wrong.

snkchrmr

Yeah throttle was open. I know its lower than it should be. I was using a cheap advance auto compression tester I have so, it could have something to do with that? The car is getting zero blow by. All the plugs still look new and zero oil in catch can or lines to it. The only thing I can think of is that the power was falling off starting around 4k or so and really dropping at 5k is because the fuel pressure had dropped to 20psi by 5k?

rotary1307cc

iTrader: (5)

get a a good gauge, do and do it properly again

if you pull 100psi cranking on all cylinders evenly again, then parts were not picked properly and no wonder the car is a dog