Vacuum Lines

[65Cobra]

Can't seem to eliminate a problem with my Gen1 running too rich at very low throttle/rpm, although I'm still working on it. I'm positive the vacuum lines are properly routed, including the lines for the MAP sensor. Tried a second check valve at the MAP sensor but no difference. No leaks...everything actually looks good, so I did some searching and have three items...

I used 5/32" (.156") ID vacuum hose thinking the original line was 4mm (.157"). But now I'm wondering if the original line was 3mm (.118") because I read where larger and/or longer lines cause signal delays. At first it doesn't seem like a lot but that's a 31% increase in ID alone and I'm definitely using more line, considering the Blow Off Valve, Vaccum/Boost Gauge, etc. Wondered if anyone could shed any light on this, or it would even help if you let me know what size vacuum hose you're using.

For anyone using a BEGI FMU... I'd like to know how much of the top center adjustment screw is above the nut. Mine is a a hair over 7/32"... and that's only 1-1/2 turns IN from the point where the screw barely makes first contact with the spring. Although I think that's pretty far out, I plan to turn mine out even further just to see what happens.

Also with the BEGI FMU, has anyone ever replaced the internal spring with a lighter one? At one point Corky was thinking of supplying a kit with a weaker spring for users that had this sort of issue... so it must be a potential fix.

Thanks

 

[POWERHOUSE]

Can't seem to eliminate a problem with my Gen1 running too rich at very low throttle/rpm, although I'm still working on it. I'm positive the vacuum lines are properly routed, including the lines for the MAP sensor. Tried a second check valve at the MAP sensor but no difference. No leaks...everything actually looks good, so I did some searching and have three items...

I used 5/32" (.156") ID vacuum hose thinking the original line was 4mm (.157"). But now I'm wondering if the original line was 3mm (.118") because I read where larger and/or longer lines cause signal delays. At first it doesn't seem like a lot but that's a 31% increase in ID alone and I'm definitely using more line, considering the Blow Off Valve, Vaccum/Boost Gauge, etc. Wondered if anyone could shed any light on this, or it would even help if you let me know what size vacuum hose you're using.

For anyone using a BEGI FMU... I'd like to know how much of the top center adjustment screw is above the nut. Mine is a a hair over 7/32"... and that's only 1-1/2 turns IN from the point where the screw barely makes first contact with the spring. Although I think that's pretty far out, I plan to turn mine out even further just to see what happens.

Also with the BEGI FMU, has anyone ever replaced the internal spring with a lighter one? At one point Corky was thinking of supplying a kit with a weaker spring for users that had this sort of issue... so it must be a potential fix.

Thanks

What is going to happen is your bike is going to run leaner. The center adjustment screw on the BEGI is for your base (idling) fuel pressure. If you have stock injectors on the bike, you should put a fuel pressue gauge on your bike, and set your base fuel pressure to 42-43 pounds at idle. The gold screw on the side adjusts "rate of gain", or how quickly your fuel pressure rises in relation to boost. This should initially be set to about 1 turn out.

These adjustments are critical to the entire map! Turn either one of those screws in or out, and you have just modified your A/F across the board. Do yourself (and your engine) a favor, and get this thing on a dyno with someone who knows how to tune a turbo . . . before something bad happens.

 

[65Cobra]

I appreciate your response Frank, so please don't think otherwise, but I intentionally asked specific questions because, over time, I found my situation doesn't fit the norm... both because of the year of my bike (1999) and some of the components I use (BEGI MR2035). I'll try to explain but it's hard for me without getting wordy. That's what people tell me anyway

I posted earlier this summer when I was trying to find a place that would update the map for my PCIII. But in the end, no-one within 3 hours of me would schedule a specific appointment or even a specific day. Instead I had to leave the bike and it would take 2-3 days in order to work on it as time permits, which means I could not be there while the work is being done. That's a problem considering these guys seem to have no idea what a BEGI is, let alone how to adjust one. All that tells me is they have no intention of doing anything other than make a map and send you on your way. I'm also not keen on the idea of leaving a turbo busa with anyone I don't know, especially places that have a taste for fast bikes... the risk of something happening is greater and they will never admit fault if anything goes wrong.

I've been using an LM-2 Air/Fuel meter and fuel pressure gauge for some time now. I started with a map from another turbo busa and have yet to find any lean conditions, although I'm keeping the bike under 6,000 rpm for now to be safe. I recently purchased additional sensors for vacuum/boost and fuel pressure in order to add them to the log but haven't installed them yet. I ride a regular route when recording, and the changes I've made to the map have worked well until now, but I want this resolved before I try any higher rpm ranges.

I've also posted about my base fuel pressure before, but my 1999 model apparently differs from most. My original fuel pump was external and the manual says to adjust the pressure to 43 psi without starting the bike... only with the ignition switch On. At idle, my pressure drops to 36 psi due to vacuum, which I understand is correct even though the manual doesn't say. Just to make sure, I tried setting my fuel pressure to 43 psi at idle, but the bike barely ran.

I've posted several times about the BEGI, but because I have the Multi-Role MR2035 unit, which incorporates a 1:1 regulator, it seems to throw everyone off. For example, this unit requires both vacuum and boost to operate properly. For one, the check valve cannot be installed in the vacuum line that runs to the R/R chamber. It can only be placed at the outlet of the needle valve, in the opposite direction, so it retains vacuum but bleeds off any boost released by the needle valve. It's no exaggeration to say I completely understand how this unit operates... how to set every adjustment and what overall affect that adjustment will have.

Although I could continue modifying the map, the last several adjustments failed to make any improvement in these last problem areas... which is why I believe there is another problem, and asked the questions I did. I'll be talking with Corky tomorrow, but in the meantime, here is where I'm at...

At this point, the R/R adjustment on my unit is only 1-1/2 turns inward from the point the R/R screw first contacts the inner spring, which barely puts any tension on the spring at all which originally led me to believe the spring is too heavy. The reason others question my logic is because this problem only occurs with a Multi-Role unit since they rely on vacuum as well as boost to operate. Problem is I've yet to find anyone else that uses this model which pretty much leaves me on my own.

Not that anyone should do this but, if you replaced the R/R spring with a slightly lighter one, it would mean less downward pressure on the diaphram. With no other changes, that reduction in spring pressure means boost has a harder time pushing the diaphram downward. The end result is less fuel pressure during boost conditions.

In my case, the Multi-Role MR2035 also requires vacuum to operate properly. With no other changes, that same reduction in spring pressure means vacuum has an easier time pulling the diaphram upward. The end result is less fuel pressure during vacuum condtions.

There are three items that convince me the spring is too heavy...
(1) R/R Adjustment
(2) Needle Valve Adjustment
(3) PCIII Map Settings

You can compensate for a slightly lighter or heavier spring by readjusting the R/R Screw and/or Needle Valve. Spring pressure is more critical on the Multi-Role unit because proper operation depends on the diaphram moving in either direction from it's center point. Since my bike is running rich during vacuum conditions, if anything I would need to turn the R/R Screw counter-clockwise, but mine is almost all the way out now. Same holds true for the Needle Valve... if I need to turn it counter-clockwise, I can't because it's already 4 turns out. In other words I've reached the limit of adjustments on my BEGI.

Add to that, I've been using negative numbers within areas of the PCIII Map where the bike hasn't even reached boost yet, and I'm back to my original questions because it's either the vacuum lines or the R/R spring... the latter of which I'll talk to Corkey about tomorrow.

Thanks... and I told you I'm wordy...

 

[65Cobra]

Although I'm still interested in any comments, I wanted to post the results of my conversation with Corky at BEGI today...

Basically my reasoning was correct but there is another culprit that is more likely causing the problem and much easier to fix... the check valve. Even when the check valve is installed correctly, one check valve may not be sufficient and can affect the transition between vacuum and boost. In my case I'm noticing the effect on the vacuum side of the transition. The solution is to install a Tee fitting and add a second check valve.

Funny, because after all the searching, no-where did I see anything that mentioned using a second check valve on a BEGI. If anyone else has had to do this, I'd be interested in knowing the circumstances.

We discussed the spring further and they did use a lighter spring at one time but later switched to the current heavier spring, but the reason he doesn't think the spring is the problem is because they tested that spring and it should be able to go down to the level I need. He did say my issue has come up dozens of times and each time the second check valve solved the problem.

Great! Now I can move on.... but still keeping my fingers crossed. I'll post the results here but it may not be until this weekend.