The Project Pad

Damn man this sucks!!!! I had hoped you might have had it solved by now! :bashtard:

well...I found a reaaaaaaaaaallllllllllllllyyyyyyyy messed up vacuum line...

...the one that goes to the MAP sensor

I checked it before, it seemed to be alright. I decided to replace all the vac lines today and kinda skipped over this little 6" section. When replacing all of the other lines didn't work, I decided to squeeze on this one while the car was running. It collapsed.

Replaced it, car runs great. AFR is still wacky at WOT but the car runs awesome so I think I'm going to put the car back on 1.1.70 and calibrate the 02 sensor again. Then make some pulls and see whats up.

I'm just glad its running well enough to get me home now. The car was definitely getting progressively worse so like I said before, don't be too quick to blame the ECU!!

Now this may well be separate from the stutter issue I was having in boost, but I won't know unless/until it comes back. For now I'm happy. Will be 100% happy when I can see the AFR in happy land too.

:woowoo: :woowoo: Rockin Chris!!! Glad to hear!!!

EDITED: Miss Post... apologies, wrong thread

You would be amazed at how much a vacuum line, especially one to the MAP sensor, can ruin your day. I'm glad you got it fixed. Can't wait to see what it'll do once it's fully tuned. Good luck.

That is awesome !! i do know how frustrating it can be .......believe me

loxx, My aeromotive fpr had a port right on the side for a gauge. 1/8" npt... done.

sweet, thanks...I guess I wont be getting one right away now that I don't have a problem, but I'll have one as soon as I start reworking the fuel system.


for future reference
OK I have some questions regarding fuel systems. The only fuel rails I know of for our cars use -6. 034 has one that "can accommodate" -10, but its tapped for 1/2 inch NPT which is about -6. Wouldn't it be pointless to run all -8 or -10 or what have you when your smallest point is a -6? Its like an orifice at that point.


I would like to use an A1000 or twin bosch 044's. A1000 uses -10. There is a FPR that is "supposed" to go with the A1000 that uses -6 and another that uses -10. So the big question is, how much power can -6 really support assuming an EFI/forced induction application? What really ends up being the limiting factor on these cars when it comes to fuel? I know on the 1.8t's they make over 600whp on the stock fuel rail lol. Sometimes what works in theory isn't quite what works in real life, so I'd like some good input if possible. [/i]

-8 is "half inch". -16 is "one inch". SAE is very common, as is JIC and NPT. There are ways to adapt from ORB to NPT, ORB to JIC, ORB to SAE, BSPP to SAE, etc etc. Personally I'd rather have SAE or JIC for a fluid fitting. We just ran 2ksi hydraulics in ORB and SAE, with a few NPT fittings here and there. Used TyLok stainless steel fittings and 0.035 seamless stainless tubing.

Well -AN (which is ORB correct?) seems to be the most common for fueling stuff these days. I just want to know what size I should get to support sky high power on gasoline.

if you are staying on gas, go -8 for "sky hi" power. if e85 is a possibility, -10. -10 will support 1000hp on e85. -8 1000hp on gas.

OK so then what about my fuel rail question? Fuel rail on your site is -6. Would that not negate any advantage gained from running -8?

-AN is not ORB. ORB is o-ring boss, AN (army-navy) is VERY similar to JIC, which is a 37d flared fitting.

out of stock on the -6 rails -8 is incoming any day to replace it (slightly higher price). A small section of -6 (like at the fittings on a fuel rail) is not as much of an impedance to flow as a long section of tight diameter tubing.

OK thanks for the explanation cuatro.


Marc, so then is radius of the internal cross section of the rail going to be equivalent to -8 (1/2 inch?)?

OK, just from a conceptual point of view it seems like frictional effects would be the only thing that would make that true. I'm not disagreeing with you, I just want to know what the heck is going on that makes it true.

I'm thinking about it like an orifice. Lets say you have a large pipe with a small orifice. Neglecting the boundary condition and thus frictional effects, I'm pretty sure that theoretically having the entire pipe the same diameter as that orifice would give the same result. So I would like to know how this translates into the real world and why.

loxxrider wrote:OK thanks for the explanation cuatro.


Marc, so then is radius of the internal cross section of the rail going to be equivalent to -8 (1/2 inch?)?

OK, just from a conceptual point of view it seems like frictional effects would be the only thing that would make that true. I'm not disagreeing with you, I just want to know what the heck is going on that makes it true.

I'm thinking about it like an orifice. Lets say you have a large pipe with a small orifice. Neglecting the boundary condition and thus frictional effects, I'm pretty sure that theoretically having the entire pipe the same diameter as that orifice would give the same result. So I would like to know how this translates into the real world and why.

there is a "reservoir" effect as well. so the larger diameter area on the other side of a slight restriction can take up small hits when flow demands exceed the limit caused by the restriction.

-6 isn't exactly small, I'd definitely be comfortable to 600hp.

when i get the kids to bed i'll comment on internal flow...can't type well while holding a 9mo old!

Hmmm I don't get it. I could see that if the fuel was compressible, but its not. If you are approaching the maximum amount of flow that the orifice can support at a given pressure, how can one overcome that?

The only thing I can see is that the pressure will increase on the feed side of the restriction as a result of the restriction. That would allow for more flow just because of the restriction itself actually and the regulator doesn't see this so you'd potentially have more pressure before the orifice but regulator pressure after it.

The new 034 rail i just got uses a -8 orb. It's a new cnc style i guess. They haven't updated the site yet. Slap some radiused -8orb's on there and you're g2g.

Seems that it would also depend on how much your pump can flow with the given back pressure that the orifice creates.

Okay...One down. The other is watching a little bit of Cars, so I have some time!

Hose has a higher surface roughness than the fuel rail. A #8 hose with a #6 hose end that is threaded into a fuel rail with an ID of 1/2" will flow almost the same amount as a #8/#8/.5". You will have a velocity spike at the connection, but the losses (while "major") are minor compared to the friction forces of the hose and rail (which are "minor" losses). If you've had Fluids yet, and have talked about quasi-one-dimensional (internal) flow you should have talked about some of this stuff, so it should ring some bells.

Really, you want as much rigid pipe as possible in any fluid system, however hose can be very convenient and certainly faster to install. The rigid pipe work, as I said, has a much lower surface roughness and therefore less minor loss factor to it.

dubsmith wrote:The new 034 rail i just got uses a -8 orb. It's a new cnc style i guess. They haven't updated the site yet. Slap some radiused -8orb's on there and you're g2g.

o-ring? Interesting.

OK so you are saying the frictional losses are going to be more important to worry about than I thought in the first place. I have indeed had fluids, so I understand everything you are saying. It definitely corresponds to what I was saying before.

The orifice will correspond with a pressure increase AND a velocity increase of course. So it does depend on how much the pump can flow vs the back pressure.

Either way, looks like I'll be using -8 and a -8 rail

You probably even could have taken the -6 rail and machined it to -8 and still had enough material for a proper seal...Either way, I don't think that spot of -6 would have limited you. Now, if you are going for 1khp, then I'd have gone with a -8 or a -10 rail...

Yeah, not shooting for 1k. I think 800 is tops for this build. I gotta take baby steps here

I don't think I'll ever really care to have anything making 1000whp. Its kinda useless in a track situation. Pretty much anything with 500whp is enough to have a hell of a lot of fun in if it has the other characteristics to go with it.