How much Vacuum?
 

Hey guys,

New member, first post. I have a brand new DSS 331 with GT40 irons, E303 cam, Cobra upper and lower and the Incon 800TTi kit. I just fired the motor for the first time this past weekend and I am having a really bad stumble / poor idle problem. I have been reading a bunch of posts about this but I figured I should start my own with my own questions!

So here goes:

1. My boost / vac meter is saying roughly 10 inches of vacuum at at idle and drops lower when I rev it? Is 10 correct?

2. I have played with the timing quite a bit but it seems to not improve anything. I have set it @ 6 degrees BTDC (recommeded by mfctr). Now my question is can the distributor be installed wrong? What I mean to say is that it is all releative position correct? As long as #1 cyl is @ TDC (compression stroke) and my pointer is pointing @ #1 in the distributor I should be good to go REGARDLESS of position of distributor? correct?

Thanks in advance!

Re: How much Vacuum?
 

Checking vacuum on a boosted car is tricky and the results should not be judged the same as a N/A car.

Good luck with your problem. That sounds like one sick ride, it should be a blast when you get the bugs worked out.

Re: How much Vacuum?
 

True but the turbos dont make boost until you put a load on them. Right now the car is sitting in the garage without load, so boost / positive manifold pressure isnt really an issue. :D

Re: How much Vacuum?
 

To give you a better answer I need a little more info:

What size are the injectors?
Engine management system, chip, or stock computer?

Your combo appears to be beyond the stock computers abilities. If you have 42lb inj or larger you will most likely have to reduce fuel pressure at idle - at the detriment to higher rpms. The 6* is hurting the idle quality slightly. I see 12-13" at idle on my combo listed. (custom mild cam). As you increase your throttle position, the car will head toward 0 vacuum until boost is present. Then you hit the other side of the boost gauge and register boost. On a NA car, under WOT, you will see 0 vacuum.

Re: How much Vacuum?
 

36 # calibrated to the mass air "tube" stock computer and FPR. My fuel pressure gauge says roughly 40. I have tried advancing the timing to 10 but it made things worse.

Re: How much Vacuum?
 

An E-cam generally will produce in the neighborhood of 15 in-hg at stock idle and 10-degrees base timing, a little more as the idle is increased towards 1000rpm. As others have said, removing base timing will affect idle and hence vacuum at idle. Have you checked your actual base timing? With the 331, load calculation by the computer will be off a little which will affect things a bit. It really sounds like you need to have the car tuned by a professional to bring the combination together and get the best all around performance.

Re: How much Vacuum?
 

I have set the base timing with the jumper pulled out as well as advanced and retarded the timing with the jumper out. I agree that the car will most definitely have to be tuned by a pro but I *should* be able to get it to running better once I verify no vacuum leaks. Last night I pulled the upper intake off and put new O-rings on the fuel injectors. I noticed that the lower intake had an oily residue on the inside. I believe this to be caused by a bad PCV valve OR leaky turbo oil seal? *IF* it was the turbo seal than I would have oil in my intercooler and the entire intake system which I don't *phew* so pretty sure its my PCV valve? Not sure how old that valve is.

Re: How much Vacuum?
 

SO here is the update:

I pulled the upper intake and valve covers off, re-did all of the vacuum connections under the intake, put brand new o-rings on all of the injectors, installed an adjustable FPR, new PCV valve and re-timed it. I also did the redneck TDC check with a "probe" in the #1 spark plug hole as I turned the motor over by hand while watching the pointer on the balancer. I have a feeling that the balancer may be off a little though in terms of being aligned correctly with the crankshaft. Is it possible to install the balancer misaligned or would it just bind at the keyway? I was able to start the car and it seemed to be pulling more vacuum and seemed to rev better (gentle revs). My fuel pressure is lower due to the FPR. What should my fuel pressure be set at?

I'll update after driving in the morning.

Re: How much Vacuum?
 

Set fuel pressure at 40psi with vacuum off. Balancer hub can't be misaligned unless the key is missing. However, the outer ring that has the timing marks can actually slip and throw you off in setting the timing. The stop in the hole isn't an accurate way to establish TDC unless you use it in conjunction with a degreeing wheel. There's too much dwell at TDC for it to be accurate.

Re: How much Vacuum?
 

Most Ford injectors are rated at 39 psi. With the vacuum source off and plugged, set the fuel pressure to 40psi. The 36's may not be enough at the high end so be carefull on getting the right tune. At an 80% duty cycle, 36's are only good to about 385hp. If fuel demand is high, and you want to tune with the injectors, I wouldn't go much higher than 50 psi. You will effectively make the 36's act as a larger injector and you'll be able to reduce the pulse width of the injector. You really don't want your injectors working routinely in the 90%+ range.

I also find that with aftermarket intakes you will have an issue with oil in the intake with the PCV system. ...Even with the correct baffles, screens and being properly hooked up. I have more info on the the injector and PCV issues on my webpage.

The balancer is on the crank with little keys - it can't be installed off a little. However, the pointer bracket could be off. You could ensure that the engine is truely at TDC and adjust the timing marker to align with the balancer. If the marker is off it will effect your timing reading...

Re: How much Vacuum?
 

Damn Jeff, you snuck in there while I was still typing...

Re: How much Vacuum?
 

OK so I have been doing some tinkering since this morning, I have adjusted the fuel pressure to 40 PSI with the vacuum line off and plugged. Fuel pressure at idle reads about 35 - 36 psi with vacuum line connected. Also, I am seeing roughly 10 - 12 inches of vacuum at idle which jumps as high as 20 inches when giving light revs. I also found that I was missing the screen under the PCV valve which was more than likely allowing oil to pass straight into the intake. So I put a screen in there. Once the car warms up it seems to idle much better however it is still not quite right in terms of running under light throttle. It stills sputters and runs sorta rough. Is it possible to check my A/F ratio without a meter? Is that a dumb question? lol ;)

Also, about the balancer, i have read posts in other forums where guys said they ruined their Romacs (which is what I got) buy installing it misaligned and basically chowing the keyway on the balancer. This happens when you install it the "hard" way which is with a balancer installer (interference fit) and not the "easy" way which is to put the balancer in the oven for a short period of time which allows the balancer to expand at which point it simply slides onto the crankshaft snout taking all the guesswork out of aligning it. I guess i should have done that the first time.

Thanks for your input so far guys. :D

Re: How much Vacuum?
 

Any balancer I have ever installed has always gone on at least part of the way by hand. Some needed to be cleaned up a little, but I would think cranking it on from the very beginning could be asking for some troubles.
Ryan

Re: How much Vacuum?
 

Let's take a different approach here. Describe your turbo kit. Is it blow through or suck through? Are you positive that you have the bypass valve correctly plumbed (vacuum modulation)? How does the bypass recirculation dump back in? Is it close to the turbo inlet or MAF? Tuning a turbo can be quite tricky.