Manifold / TB rule revisions

Z3_GoCar

Z3_GoCar

New member
I'm confused by all this Intake manifold/throttle body revisions to the ST rules... Can someone explain what's going on?

Also, what if there are two possible Intake manifold that came in your car with two different numbers of throttle bodies. Are you trying to limit us to the most common one with the minimum number of throttle bodies? I'm just not sure what you're trying to do wrt the rules.
 
Z3_GoCar said:
I'm confused by all this Intake manifold/throttle body revisions to the ST rules...
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Specifically what regs are you referring to?

If you swap engines, you can use the intake that was on the engine you installed or the car you installed it into.

- GA
 
Greg Amy said:
Specifically what regs are you referring to?

If you swap engines, you can use the intake that was on the engine you installed or the car you installed it into.

- GA
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It's under the section just added last month 9.1.4.G.1.e.1:

1. Regardless of the intake chosen, the total number of throttle bodies must remain the same.

The same as.... the chassis, the motor, or??? My chassis has two different generation motors installed in it along with about seven different motors, one of those has a two barrel throttle body, five have a single barrel (some are cable operated and some are electro-servo,) and one has six throttle bodies. All of these motors are in my dealer sourced shop manual, and are USDM.

Any insight into what this means? Thanks Greg.

James
 
Z3_GoCar said:
The same as.... the chassis, the motor, or???
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Good point. The rule stems from someone - a BMW driver, of course, trying to install a 4-choke ITB intake onto an otherwise-STU compliant engine, that would have provided a distinct competitive advantage. I'll bring this to Eric Heinrich's attention, he can explain more.

If we need to, we'll adjust the verbiage.

- GA
 
The "writing a rule to prevent something specific" trap. I believe that's Ad Hoc committee standard error 37.1...?

:)

K
 
Greg Amy said:
Good point. The rule stems from someone - a BMW driver, of course, trying to install a 4-choke ITB intake onto an otherwise-STU compliant engine, that would have provided a distinct competitive advantage. I'll bring this to Eric Heinrich's attention, he can explain more.

If we need to, we'll adjust the verbiage.

- GA
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The advantage comes from part throttle driveability, every builder I've spoken with agrees that moving a single TB further away from the head can make the same power as ITB's.

Regardless, the point of the rule wording was because initially it was completely in conflict with it self - originally the rule said you had to keep the original intake manifold unless you changed it in which case you had to keep the original intake manifold. I"ll take a closer look tonight at the wording and what's being asked here and post my thoughts.

One thought I have had is, given the FI car's continuing dominance inspite of weight and restrictor adjustments, I think N/A cars should have more freedom to play with the intake manifold than they do, but I'm pretty sure that idea would be DOA.
 
I'm with Eric, and have been on record thinking the same (and more) for well over a year.

in a displacement to weight class with street car origins, using street car parts is a very good way to separate the haves from the have-nots. FI will overcome a lot of those issues and, especially with the more modern turbos, sacrifice a touch of peak hp for huge gains in area under the curve over a NA sibling, even with small restrictors. couple that with a huge industry-wide shift (more true in smaller STL type engines but still) toward low end torque and efficiency over performance, and you get a similar enhancement to the NA cars but a lot less peak power potential in most cars than in a few exceptions. yes, hp/L numbers have been on the rise, but once the rules are factored in a lot of that dies off in lost "gains" and you're often times left with a relatively shitty (for racing) intake and head designed to get 11ty MPG on 7-11's 87 octane. NA generally can't compete with FI under that basic premise. open the rules and let the displacement be the driving force like it's supposed to be (at least more so), and fields will be a lot more diverse, and yes, maybe more expensive. and the gap to FI should shrink.
 
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Chip42 said:
I'm with Eric, and have been on record thinking the same (and more) for well over a year.

in a displacement to weight class with street car origins, using street car parts is a very good way to separate the haves from the have-nots. FI will overcome a lot of those issues and, especially with the more modern turbos, sacrifice a touch of peak hp for huge gains in area under the curve over a NA sibling, even with small restrictors. couple that with a huge industry-wide shift (more true in smaller STL type engines but still) toward low end torque and efficiency over performance, and you get a similar enhancement to the NA cars but a lot less peak power potential in most cars than in a few exceptions. yes, hp/L numbers have been on the rise, but once the rules are factored in a lot of that dies off in lost "gains" and you're often times left with a relatively shitty (for racing) intake and head designed to get 11ty MPG on 7-11's 87 octane. NA generally can't compete with FI under that basic premise. open the rules and let the displacement be the driving force like it's supposed to be (at least more so), and fields will be a lot more diverse, and yes, maybe more expensive. and the gap to FI should shrink.
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Chip..

submit a letter. otherwise it's just an idea that's on some forum somewhere.

www.crbscca.com
 
I pretty much agree with both guys above-- I've been bitching about the stock IM for quite a while now..

for my 240, it was either go FI with a JDM engine, or go slow forever on the stock intake manifold. The old SpeedVision guys were making ~220whp with that engine built to their specs, which was about same as the current STU specs. Sorry, I need another 50hp to be able to even think about keeping up in a 2.4L.

... So I went to an EP rotary.. It's cheaper there. ;) (yes, I'm going to keep fooling myself with that until I blow up my first engine..)
 
So while are - once again - bitching about turbos versus non-turbos in STU, can someone take a quick moment to answer the man's question...?

Jeebus.

- GA
 
Eric - I wrote in with my thoughts about the general idea of the class when it was reimagined a few years ago. the path I like and the path the club chose to go were pretty significantly different. yes, I've been vindicated on some occasions but other than following along at home and perking up here very now and then I don't participate on any level in ST, so wont be writing in (I'll let those with skin in the game ask for such things). I have refocused on IT where I'd been playing in some form or another since the early 90s. I am on the ITAC, and appreciate the "write a letter" comment as it is what we should be doing with our ideas.

tGA - I think Eric did, to the best of his ability. the OP's question is valid, the rule doesn't make sense. might be that you STAC guys can shed light on how it came to be but clarifying it does seem to be improbable.
 
Chip42 said:
I think Eric did, to the best of his ability. the OP's question is valid, the rule doesn't make sense.
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Completely concur. I don't remember the origin of the reg; it was something Eric brought up as a distinct possibility in reference to a letter/request, and another committee member said something like "let's just say you gotta keep the same number of throttle bodies" and we said "Ok, sounds good; next question"...

Honestly, as Kirk pointed out, this is kinda chasing our tails. We cannot possibly think of all situations and make individual rules to account for each...

- GA
 
Bringing back some part throttle response would be great, because if I were to cam my 2.5 liter motor as much as I would need to, I'd have to disable the intake vanos which would really kill any midrange. Think stuck in V-tec.... yoooooooOOO!
 
Matt93SE said:
I would if I could. but I can't. and if the STAC members can't even answer it...... :023:
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Well, here's MY answer (note the signature).

If you install a STU-compliant 4TB engine into a STU-compliant 1TB car, you can run the engine's 4TB intake. If you install a STU-compliant 1TB engine into a STU-compliant 4TB car, you can run the 4TB intake. And, per the regs, you can build a 1" spacer to make it all fit.

Now, WTF this all means in the very unhappy world of BMW owners is beyond me (and, very quickly, going beyond my interest).

Eric had a reason for bringing this up in committee; if we can't remember why, then the point is moot.

- GA
 
What makes the rule ambigous is somehow the words "for the installed engine" got left off of the TB limitation.

Therefore, the BMW in question would not have the option (assuming 6cyl) of using the ITBs from an engine that is not allowed in STU, even though it came in his chassis at some point in time.

I will submit a letter to get this clarified
 
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