[DrGT500]

Ok, being new to the GT500 specifically, and supercharged cars in general, I have some questions and I was hoping some of you guys that have been around this car and modded them can school me here.

My questions relate to available boost pressure vs. gear selection and also, in a related area, what mechanical means (if any) are used to limit boost? I've had a couple turbo cars and boost was regulated by vacuum controlled blow-off valves and I was wondering if/how Ford accomplishes the same/similar function on our engines?

The reason I ask is this. While I realize it's purely anecdotal and not a "reliable" measurement, I've noticed that apparantly in first gear, the engine seems to be limited to ~5-6psi of boost according, at least, to the in dash boost gauge. Now, that said, as soon as I shift to second (or higher) and get into it, the boost gauge will climb to an indicated ~10psi of boost.

So, I guess what I'm asking is, simply, does the ECU limit us to something less than "full boost" in first gear? I can understand this would make sense due to traction issues. And, if so, what method does the supercharger use to limit boost. I know that pulley size mechanically regulates the absolute upper limit of boost the SC can produce by controlling how fast it can spin, but there must be some secondary mechanism for boost regulation that's controlled by the ECU, isn't there?

Sorry for what are probably elementary questions. I hesitated to ask for fear of being taunted relentlessly now and forever more. lol Yet, asking I am. Have mercy on me.

Regards.

 

[milezperhour]

1. first gear is useless...
2. why would you want boost in first gear anyway...
3. i'd expect you'd over rev anyway in lower gears...
4. i don't even go into boost in second when going from the line...
5. not sure..

 

[DrGT500]

1. first gear is useless...
2. why would you want boost in first gear anyway...
3. i'd expect you'd over rev anyway in lower gears...

I agree about boost in first. You'd just spin. I was asking mainly because I wanted to ensure that the way MY car was functioning was "normal". Remember, I have no history with these cars. Didn't know anyone with a GT500. I just wanted to make sure that the behavior I'm seeing is normal and expected.

4. i don't even go into boost in second when going from the line...
5. not sure..

Me either, but that's why I was asking. I was hoping to hear from someone here who might. I'm guessing it might be some sort of internal bypass in the SC that would limit boost? There has to be some sort of internal bypass because when you're just cruising (low-vacuum) you get no boost. Even with my limited knowledge of SC's, I know with purely mechanical "Old-school" roots-style blowers, when you spin 'em you made boost. lol

Anyway, thanks for the reply. I hope to hear more.

Regards.

 

[6-Speed]

The GT500 Eaton blower has an internal bypass that's vacuum driven.

 

[DrGT500]

The GT500 Eaton blower has an internal bypass that's vacuum driven.

Mucho Gracias, amigo. So, am I correct in assuming that the low(er) boost I see in first gear was the way the system was designed to work?

Thanks.

 

[WA 2 FST]

Mucho Gracias, amigo. So, am I correct in assuming that the low(er) boost I see in first gear was the way the system was designed to work?

Thanks.[/QUOTE

Unless there is an electronic valve attached to the bypass valve, then the ECU is not pulling boost in lower gears. I do know on the older vehicles (SVT Lightning/SVT Cobra) the ECU can open up the valve in a "limp mode" state if some specific malfunction codes get thrown. But the ECU doesn't typically have any control over this mechanical valve unless there is a problem.

Most likely, since you have very little traction in 1st gear, the engine is not under full load, therefore it will never reach its maximum boost capabilities in that gear, unless you run a sticky tire. As you know with your previous turbo cars, the engine has to be under load in order for there to be positive manifold pressure. Tirespin will drastically reduce engine load, even as the rpms climb, and if you're feathering the throttle at all, you'll see boost drop or just maintain a lower pressure.

 

[DrGT500]

So, Wa-2-Fast..

I couldn't stand it. I read what you wrote and it made perfect sense when I thought logically about it. Sooooo... I took her out and rode that thing like a rented mule! You were right, the boost was there for the taking all along. I just wasn't getting into the throttle enough/long enough.. to see it. I'm definitely getting full boost in first gear. I might also be needing to get new tires soon if I don't knock that off. But, just let me say for the record... DAMN that blower whine is ADDICTIVE. *sheepish grin*

:rofl:

 

[WA 2 FST]

:rofl: Sweet!!!