Andy Bettencourt
Super Moderator
Yes.
Hopefully some improvements will be made with legal porting but gee-whiz Chevy!!!
ITAC News.
- Thread starter lateapex911
- Start date
Yes.
Hopefully some improvements will be made with legal porting but gee-whiz Chevy!!!
lateapex911
Super Moderator
it's funny, when you say that I might agree but I have NO idea what you mean by it, in this case! One mans common sense isn't always anothers LOL
Ron Earp
Administrator
Or at some point actual research has to be done instead of guessing based on other completely different motors.
I've done a little research on the C4 and I think it has a lot of potential.
We all make educated guesses based on our experience. My experience tells me that large displacement two valve motors in IT-trim always impress with gains. I'm impartial to your ITR build as I'm not funding it, racing against it, or planning to build one - in fact, I wrote a letter asking to have it classed. I feel that common sense indicates it should weigh more than similarly powered Camaros and Mustangs that have poorer suspensions, but that is just my opinion and realize it has no foundation in IT-land.
Last edited:
benspeed
New member
Thanks Chip. I'll rustle up performance/dyno data on the S2 and the E36. Those cars are making the same power and weigh much less. Proud to submit my build sheet - been a very comprehensive process with top Porsche shops. My beef isn't about power, it's about weight.
Its very interesting to watch the experts work out how a car is classed on this thread, but it also makes me scratch my head and consider how poorly I can play this aspect of the game, hence my joke about paying an expert a retainer to help lobby my case
lateapex911
Super Moderator
Ben I know your tongue is in your cheek. But....the classing thing should be pretty much streamlined and automated.
The ITAC has, and continues to, use a process that considers basic variables, the cars stock hp and spits out a number. That number assumes several things, like an expected built horsepower.
Trouble starts when things don't line up.
Your car, and most Porsches, really, are classic examples. Most just don't make the presumed 25%. (The RX-8 is another, but it is opposite what earlier rotaries did, which was vastly exceed the 25% assumption. Real numbers were dug up for that classification, and they came from outside the IT world, and there was an extremely high degree of confidence in the evidence.)
In cases like yours, you're really trying to prove a negative. And that gets tricky. You've got skin in the game, and even though we all know you're a good guy, and the ITAC assumes you are too, you can see the obvious conflict of interest that arises.
So, in order to overcome that, you'll need to be exceedingly forthright, and show how you have turned over every possible stone. AND, if you can provide OTHER builds of separate cars, that helps your case.
Its a frustrating situation from both perspectives. But, I assure you, there's no 'game' needed. The ITAC is pretty by the book.
The ITAC has, and continues to, use a process that considers basic variables, the cars stock hp and spits out a number. That number assumes several things, like an expected built horsepower.
Trouble starts when things don't line up.
Your car, and most Porsches, really, are classic examples. Most just don't make the presumed 25%. (The RX-8 is another, but it is opposite what earlier rotaries did, which was vastly exceed the 25% assumption. Real numbers were dug up for that classification, and they came from outside the IT world, and there was an extremely high degree of confidence in the evidence.)
In cases like yours, you're really trying to prove a negative. And that gets tricky. You've got skin in the game, and even though we all know you're a good guy, and the ITAC assumes you are too, you can see the obvious conflict of interest that arises.
So, in order to overcome that, you'll need to be exceedingly forthright, and show how you have turned over every possible stone. AND, if you can provide OTHER builds of separate cars, that helps your case.
Its a frustrating situation from both perspectives. But, I assure you, there's no 'game' needed. The ITAC is pretty by the book.
This is why I support a DW adder - it's not much, but it's something. vs the pony cars it adds up to 100 lbs which is in the range of 3%, or a half step in the process gain.
and keep in mind that the CRB hasn't made a decision on the vette as recommended. they could just as easily come back and say "no way" or "add weight". at which point, hopefully, we'll have this eval done and, with more data from interested parties (hint hint: crbscca.com), be able to reply with "yeah we looked deeper and think X about the vette" or "no, the rest of ITR needs the following adjustments:...". or maybe "we researched it, it's all good, that thing's a sheep in wolf's clothes, stop thinking with your eyes." (likely a hybrid of all of these)
Andy Bettencourt
Super Moderator
Right, because that transverse leaf-spring technology is state of the art!!!!
And good luck with that CRB thing...
Last edited:
benspeed
New member
Yo Jake - yes, tongue in cheek. I suppose I shouldn't say I'm bad at playing the classing game but rather I lack the knowledge to make a solid case for less weight to get a little closer to the cars I race against. I'm just your typical driver looking to get more competitive. Chip is right - empiracal data must be collected by me to make a solid case. I'm not sure where to get it, but hey, gotta give that a shot and I might learn a thing or two in the process.
Andy - I will be sure to run my stuff past you and pay a nominal fee
(Greg, that sausage anology was perfect)
Andy - I will be sure to run my stuff past you and pay a nominal fee
(Greg, that sausage anology was perfect)
JeffYoung
New member
Been looking for flow numbers on this manifold. Found a 572 cfm number for the two throttle bodies.
For the intake found 178 CFM at 28". Is that 28" a manifold pressure number? Or is it at a certain valve lift?
I have flow at various valve lifts as well and it is GOOD but hard to tell if that was done with the intake on it or not.
I've also seen pictures of the ports and it LOOKS LIKE the restriction that GM clearly just fill welded in stops less than 1" in. You may get some good gains with an IT legal gasket match/port job.
For the intake found 178 CFM at 28". Is that 28" a manifold pressure number? Or is it at a certain valve lift?
I have flow at various valve lifts as well and it is GOOD but hard to tell if that was done with the intake on it or not.
I've also seen pictures of the ports and it LOOKS LIKE the restriction that GM clearly just fill welded in stops less than 1" in. You may get some good gains with an IT legal gasket match/port job.
lateapex911
Super Moderator
Can you link those pictures??? That is very interesting
JeffYoung
New member
Numbers here:
http://members.shaw.ca/corvette.84/crossfire.html
Pictures here:
http://users.swko.net/~lionsden/crossfire.htm
About halfway in is a comparison of the manifold "blocked" (on the right) and "unblocked" (on the left). Look at the unblocked one. The runner drops away quickly from the port. Appears that block really couldn't extend much into the manifold given the sharp taper down.
http://members.shaw.ca/corvette.84/crossfire.html
Pictures here:
http://users.swko.net/~lionsden/crossfire.htm
About halfway in is a comparison of the manifold "blocked" (on the right) and "unblocked" (on the left). Look at the unblocked one. The runner drops away quickly from the port. Appears that block really couldn't extend much into the manifold given the sharp taper down.
Last edited:
JoshS
New member
IIRC, and I'm pretty sure I do, they all have a 100lb torque adder. The 50lb difference on the one line is due to lousy brakes.
jeff - 28"(of Hg/Mercury, about 1atm or of water/H2)/wc, about 1psi or ~0.07atm) is a barometric pressure reading, indicating the test pressure differential applied to the measured item (i.e. head or manifold) which induces the flow of air. kinda like voltage for amps, temperature for heat, etc...
the "numbers" page you found shows 182/137 cfm in/ex at 28"Hg and 0.400" lift, which is close to the max valve lift also shown on that page. based on the pictures you supplied, I'd say you're right about the potential for significant flow gains.
Andy, my admittedly limited experience with the CRB has been one of good cooperation and support. I know you have had bad experiences. I hope that maybe you got them to see the light, so to speak, but no matter, I appreciate your efforts, help, and jaundice.
the "numbers" page you found shows 182/137 cfm in/ex at 28"Hg and 0.400" lift, which is close to the max valve lift also shown on that page. based on the pictures you supplied, I'd say you're right about the potential for significant flow gains.
Andy, my admittedly limited experience with the CRB has been one of good cooperation and support. I know you have had bad experiences. I hope that maybe you got them to see the light, so to speak, but no matter, I appreciate your efforts, help, and jaundice.
the spreadsheet shows -50 for brakes, -50 solid axle, and +150 torque on the 89-93/94-95 mustangs, same without brake adjust on the 87-92 camarobirds. they all use a 30% gain and all match the GCR. mustang weight difference is the result of 10hp: (10*1.3*11.25=146.3)
the only +100 tq adder in there is for the V6 94-98 'stang
this is the doc from Kirk Knestis, created march 2008 (thanks to KK for this)
JeffYoung
New member
Got it on the 28" -- thanks.
THe other thing with these era FI systems - the fuel and timing curves are all screwed up for economy and emissions. You'll see big gains once you start correcting that.
Agreed on the CRB -- since about February of 2010, we have all worked well together. Jim Wheeler, Bob Dowie, Chris Albin, Peter Keane, Jim Drago -- all supportive and helpful.
THe other thing with these era FI systems - the fuel and timing curves are all screwed up for economy and emissions. You'll see big gains once you start correcting that.
Agreed on the CRB -- since about February of 2010, we have all worked well together. Jim Wheeler, Bob Dowie, Chris Albin, Peter Keane, Jim Drago -- all supportive and helpful.
Z3_GoCar
New member
Let not one person on this forum complain again that the ITAC works behind closed doors in smoke-filled rooms...
There's a reason you don't want to watch sausage being made.
I bet you posted that while behind closed doors in a smoke filled room.
Welcome to Las Vegas, I hope the wind wasn't too bad while you were outside.
Ron Earp
Administrator
V6 94-98 Mustangs are in ITS. They shouldn't appear on a ITR sheet.
94/95 V8 Mustangs have good brakes in Pony car land, four wheel discs. They shouldn't get a deduct for poor brakes. Was the ITAC giving deducts for poor brakes?
Ron Earp
Administrator
Interesting.
I see a cam duration that is somewhat okay at .050" lift, about what I'd expect and what I have to deal with on my own car. Valve lift isn't bad at all on a per cylinder basis and given the size of the valves, 1.94" and 1.5", typical Chevy sizes. Stock the throttle bodies flowing around 572 cfm isn't too shabby at all. If those head flow values are worth a damn then that is pretty good stock, quite good. I suppose we'll never know if the flow values are with the intake in place or not. Those boys are doing some trick work boring those throttle bodies out. Clearly illegal on the latter but I'd also say unnecessary based on the stock flow and other components in the engine.
All in all, impressive. I'd build it!
Last edited:
it's an IT sheet. just making a point.
yes. the spreadsheet has a -50 in the brakes column, ops manual calls out the same (+ or - depending). I suppose that they were seen as small or ineffective - we'll have to keep digging for that justification.
Andy Bettencourt
Super Moderator
There are some conspiracy theorists that Chevy intentionally screwed the heads and kep the intake crappy so that the revision with TPI would look that much better. Not sure how much I buy into it but the heads are CLEARLY blocked. A new upper to that intake would have done a world of good to...it was developed...just not used.
This car will be interesting for sure. Not worried about torque at all. It's revs and HP...and brakes.
This car will be interesting for sure. Not worried about torque at all. It's revs and HP...and brakes.