A word from the CRB on the recent changes...
- Thread starter lateapex911
- Start date
Bill Miller
New member
Greg said:
Greg,
I don't know if you really don't have much information about these cars, or are just trying to pull the wool over everybody's eyes. Not much difference between a stock 189 CRANK hp motor and an IT-prepped 200+ WHEEL hp motor? Yeah, ok, I buy that.
As far as Andy's experience w/ 2nd gen. RX7s, are you familiar w/ Nick Leverone's car? That car was run out of Andy's shop. So yeah, I think he's got a bit of experience w/ a top 2nd gen. RX7.
Greg,
I don't know if you really don't have much information about these cars, or are just trying to pull the wool over everybody's eyes. Not much difference between a stock 189 CRANK hp motor and an IT-prepped 200+ WHEEL hp motor? Yeah, ok, I buy that.
As far as Andy's experience w/ 2nd gen. RX7s, are you familiar w/ Nick Leverone's car? That car was run out of Andy's shop. So yeah, I think he's got a bit of experience w/ a top 2nd gen. RX7.
Andy Bettencourt
Super Moderator
I don't currently, but did. We have one team car and one arrive and drive car in our shop now. RX-7's are popular in the NE for a couple reasons: Good support by us, no top E36's, cheap donors.
I disagree with you in this respect: There is just as much difference in an IT-prepped E36 2.5 as there is in almost every other piston-based engine in IT. 25% more power than stock is 25% more power. Just because at the stock hp levels - and the spec weight of 2850, the can can be competitive, doesn't make it an easier ENGINE to build, just a rediculously favorable classification.
Frankly, all you have to do to the rotory, is strip the junk off of it, put the latest exhaust on it, adjust the fuel pressure to your set-up, and you are 90% there. No internal allowances by the rules makes for a simple and RELATIVELY inexpensive build. Sometimes, you just have to know what you alooking at before it becomes 'simple'.
Please answer my question above, in order to be judged by the same power to weight as everyone else in the class, would you like to be unrestricted at 3100-3150 or restricted at the current weight?
dj10
New member
AB,
I'm worried that no one has given us any data and keep using the usless "Crank HP" numbers. I'm getting ready to spend $400.00 on something that has no test numbers only in theory!
I want to know what rwhp you guys want us at! This is useful hp and I don't want percentages, I want actual numbers. If this doesn't work or we have to spend more money on a different size SIR, is everyone in ITS going to throw money into SCCA to reimburse us for pissing away our money...........I didn't think so! I hope like hell some thought of this and did their homework! We will have to spend more money on this other than the SIR itself.
a nervous dj
I'm worried that no one has given us any data and keep using the usless "Crank HP" numbers. I'm getting ready to spend $400.00 on something that has no test numbers only in theory!
I want to know what rwhp you guys want us at! This is useful hp and I don't want percentages, I want actual numbers. If this doesn't work or we have to spend more money on a different size SIR, is everyone in ITS going to throw money into SCCA to reimburse us for pissing away our money...........I didn't think so! I hope like hell some thought of this and did their homework! We will have to spend more money on this other than the SIR itself.
a nervous dj
Andy Bettencourt
Super Moderator
Actually DJ, one could argue that the WHP numbers are the ones that are useless. Think of the multitude of NON-engine factors that go into improving your hp to the wheels. What kind of dyno are you using? Dynojet? Mustang? Dynapak?
This is why we use dyno numbers as data for trending, not a primary source of info, it can be so flawed. There are no stock WHP numbers posted anywhere so we have to use crank numbers throughout the process.
One look at the stock hp levels of the E36 and it was obvious that compared to other cars in ITS, it was light, VERY LIGHT. When the standard 25% improvement with 100% IT-prep is applied, you get 236 crank hp. Following the process through to it's conclusion, the Bimmer would have to weigh between 3100 and 3150 (depending on adders) to fit with the other cars.
The FP restrictor is cheatable. Hence the SIR. I understand your hesitance on it's effectiveness, but you have heard here that it will actually be better for your car than a FP or the weight - if it is sized right...and the CRB is confident that the formula for sizing these things (which is proven) has nailed it. Buy the modular one from Raetech. Then you only will have to buy the insert to change up.......
.....because if the SIR chokes you down to below 220hp (or maybe 180whp on a dynojet - estimate - you decide what whp is your target given 220chp) a resize SHOULD be considered - and I will push for that.
BUT...should you determine that it is too large and you are above that magic number of 220chp, you will write that same letter to the CRB asking them to DOWNSIZE your SIR, right? Riiiiiiiiiiiiiggggghhhhhttttt.
dj10
New member
This is why we use dyno numbers as data for trending, not a primary source of info, it can be so flawed. There are no stock WHP numbers posted anywhere so we have to use crank numbers throughout the process.
One look at the stock hp levels of the E36 and it was obvious that compared to other cars in ITS, it was light, VERY LIGHT. When the standard 25% improvement with 100% IT-prep is applied, you get 236 crank hp. Following the process through to it's conclusion, the Bimmer would have to weigh between 3100 and 3150 (depending on adders) to fit with the other cars.
and the CRB is confident that the formula for sizing these things (which is proven) has nailed it. Buy the modular one from Raetech. Then you only will have to buy the insert to change up.......
.....because if the SIR chokes you down to below 220hp (or maybe 180whp on a dynojet - estimate - you decide what whp is your target given 220chp) a resize SHOULD be considered - and I will push for that.
BUT...should you determine that it is too large and you are above that magic number of 220chp, you will write that same letter to the CRB asking them to DOWNSIZE your SIR, right? Riiiiiiiiiiiiiggggghhhhhttttt.
AB, where are you getting crank hp numbers? Are you taking published factory hp numbers and adding a percent to them? That is theroetical not factual. I have no way of knowing how much crank hp I have, therefore I wouldn't write to anyone. I can only tell or show you my rwhp and what kind of dyno I used like I did when I sent you my dyno sheets last year. Right? So why not go the NASA way and require everyone to have signed dyno sheets? We know Dave so I will getting mine from Raetech. I would like to see published Crank Dyno numbers, you know where they are?
dj
One look at the stock hp levels of the E36 and it was obvious that compared to other cars in ITS, it was light, VERY LIGHT. When the standard 25% improvement with 100% IT-prep is applied, you get 236 crank hp. Following the process through to it's conclusion, the Bimmer would have to weigh between 3100 and 3150 (depending on adders) to fit with the other cars.
and the CRB is confident that the formula for sizing these things (which is proven) has nailed it. Buy the modular one from Raetech. Then you only will have to buy the insert to change up.......
.....because if the SIR chokes you down to below 220hp (or maybe 180whp on a dynojet - estimate - you decide what whp is your target given 220chp) a resize SHOULD be considered - and I will push for that.
BUT...should you determine that it is too large and you are above that magic number of 220chp, you will write that same letter to the CRB asking them to DOWNSIZE your SIR, right? Riiiiiiiiiiiiiggggghhhhhttttt.
[snapback]72481[/snapback]
[/quote]AB, where are you getting crank hp numbers? Are you taking published factory hp numbers and adding a percent to them? That is theroetical not factual. I have no way of knowing how much crank hp I have, therefore I wouldn't write to anyone. I can only tell or show you my rwhp and what kind of dyno I used like I did when I sent you my dyno sheets last year. Right? So why not go the NASA way and require everyone to have signed dyno sheets? We know Dave so I will getting mine from Raetech. I would like to see published Crank Dyno numbers, you know where they are?
dj
Joe Harlan
New member
Now thats funny.....You can't cheat a dyno.....
DJ, it has been explained for 12 pages now, Bite the bullet buy the SIR and be done with it. If you know David call him and he will give you the complete rundown. Going to certified Dyno's only works if we all go on the same day and run at the same time in the same location. Those numbers are all based on correction factors very similar to the proven 25% estimations the ITAC is working with. What you are not doing while complaining here is getting that SIR mounted in your car so you can do the testing needed to know in the end you will be just fine.Bill Miller
New member
Why's that dj, nobody w/ an engine dyno around you?
BTW, would you please answer Andy's question. If YOU could decide, would it be 3100-3150# w/ no restrictor, or 2850# w/ hp limited to 220 (crank hp) by an SIR?
dj10
New member
Those numbers are all based on correction factors very similar to the proven 25% estimations the ITAC is working with. What you are not doing while complaining here is getting that SIR mounted in your car so you can do the testing needed to know in the end you will be just fine.
Hmmmmmm proven 25% estimations. What a contradiction of terms.
Joe, your right at this point I am left with no option other than going to NASA if I want to continue to race SCCA. So I hope you are right and things will be fine.
[snapback]72491[/snapback]
[/quote]Hmmmmmm proven 25% estimations. What a contradiction of terms.
Joe, your right at this point I am left with no option other than going to NASA if I want to continue to race SCCA. So I hope you are right and things will be fine.
i'll take the weight for now. and after i do some dyno work on the car i'll let you know if i want the weight or the SIR.Joe Harlan
New member
Originally posted by dj10@Jan 27 2006, 09:29 AM
Hmmmmmm proven 25% estimations. What a contradiction of terms.
Joe, your right at this point I am left with no option other than going to NASA if I want to continue to race SCCA. So I hope you are right and things will be fine.
[snapback]72498[/snapback]
Yep, your right but I have been working on estimations for years and they have proven to be pretty accurate...
Bill Miller
New member
Well there you go dj, you wouldn't race the car at the weight that's determined by the same process that's applied to everyone else. So, what you've said, is that you want to be treated differently than everyone else. About the only thing I can say to that, is have fun racing w/ NASA and BMWCCA.!
There's another comment about door knobs, but I'll leave that one out.
Andy Bettencourt
Super Moderator
DJ,
The entire process is based on crank hp numbers - and assumptions. To date, the estimations and assumptions have been extreamly successful. In some cases, we have dyno sheets that prove or disprove certain assumptions.
Take the 12A RX-7 for example. 101 hp stock IIRC. Guess what? This is an ITC car all the way! But we KNOW, based on dyno info, that these cars can make over 150 crank hp. How? We use a commonly accepted 18% drivetrain loss and work backward from 125whp - a well documented - and sometimes conservative number. That is a 50% increase over stock.
Same issue with the hot CRX in ITA. 108hp stock IIRC, and 125whp on a dyno in legal, top-of-the-line form. Using a fwd correction factor of 15%, you can get the crank numbers pretty close. Not exactly, but as close as you can.
Now the BMW does not use any secret formula. It's the same for everyone else. 189 * 1.25 = 236. This number is supported, almost to the hp, by a dyno sheet sent in by a BMW owner who was disputing the 225whp numbers being thrown around - using the same process and assumptions detailed above.
You may not agree with the way we are doing it, but understand that we do it for everyone - the same way. We do it to determine mon weights for new cars and we do it to determine new weights for reclassifications.
So the net/net? ITS has a target power to weight in IT-prep of 12.9:1. Our data shows that AT LEAST 240 crank hp is possible. That is too much for ITS, and in unrestricted form, has had an impact on the class, both in reality and in perception.
You can either run the weight you are supposed to to fit, or get an SIR. The other cars in the class are already at the weight they should be to fit, or they would hev been adjusted. ALL USING THE SAME METHODS.
The ONLY issue on the table is if the SIR is sized properly. That is something the CRB is VERY confident of given experience and research.
AB
dj10
New member
You can either run the weight you are supposed to to fit, or get an SIR. The other cars in the class are already at the weight they should be to fit, or they would hev been adjusted. ALL USING THE SAME METHODS.
The ONLY issue on the table is if the SIR is sized properly. That is something the CRB is VERY confident of given experience and research.
AB
From what you are saying, the person with the unbelievable 225whp is really going to get hosed unless he and his "et" motec are able to tune in more hp. I am assuming they have a programable system since no engine builder I know has ever got this out of a legal 325.
I like Lytle's suggestion, make everyone run a SIR! Misery loves company.
The ONLY issue on the table is if the SIR is sized properly. That is something the CRB is VERY confident of given experience and research.
AB
[snapback]72518[/snapback]
[/quote]From what you are saying, the person with the unbelievable 225whp is really going to get hosed unless he and his "et" motec are able to tune in more hp. I am assuming they have a programable system since no engine builder I know has ever got this out of a legal 325.
I like Lytle's suggestion, make everyone run a SIR! Misery loves company.
Joe Harlan
New member
Originally posted by dj10@Jan 27 2006, 12:46 PM
From what you are saying, the person with the unbelievable 225whp is really going to get hosed unless he and his "et" motec are able to tune in more hp. I am assuming they have a programable system since no engine builder I know has ever got this out of a legal 325.
I like Lytle's suggestion, make everyone run a SIR! Misery loves company.
[snapback]72520[/snapback]
DJ, I think you are just screwing around now. But let me say this. Even with the Motec you are NOT going to tune around the SIR by more than 1 or 2 HP at best. An engine is an air pump it needs air to make power. The beauty of the SIR is it stops air flow (goes sonic) at a designated place ( bsed on displacement and other factors you'll have to research yourself) in the power curve. SO you can build a 280CHP engine but the SIR will hold it to 215 to 220 as stated. Now as far as other car needing it I don't believe it was ever designed to be a way to keep cars inside a rules set. The SIR can be cheated with compression and cams. Those things are already illegal in IT and require a protest to catch. You can bet that if I see an E36 pulling down the straight the same way they used to I will be writing a big check. The SIR is not a magic bullett it is another tool to put cars together that otherwise may not fit. As stated before the E36 is that car and the choices i could see were kick it out, move all the other ITS cars to ITA and we know crap flows down hill so I guess the 510's and rabbits wouldhave to disappear. Or use technology to work it out. I am impressed with Mr. Lytles attitude and I would offer any help I could give via the phone to help his development but I think if people are realistic they will add this unit in front of the maf snap a cone filter to the end of it and go to the dyno. I would then lay the dyno sheets side by side and I think you will see the computer compensates up to the point the engine runs out of air. I made that offer in one of these threads that anyone that want to go to the dyno for a half day that I would go along and help to tune or what ever I can offer at the dyno. I charge 75 bucks an hour shop rate for my time and I would donate that to prove this works. Now any of you eastcoasters would have to cover airfare also..
dj10
New member
DJ, I think you are just screwing around now. But let me say this. Even with the Motec you are NOT going to tune around the SIR by more than 1 or 2 HP at best. An engine is an air pump it needs air to make power. The beauty of the SIR is it stops air flow (goes sonic) at a designated place ( bsed on displacement and other factors you'll have to research yourself) in the power curve. SO you can build a 280CHP engine but the SIR will hold it to 215 to 220 as stated. Now as far as other car needing it I don't believe it was ever designed to be a way to keep cars inside a rules set. The SIR can be cheated with compression and cams. Those things are already illegal in IT and require a protest to catch. You can bet that if I see an E36 pulling down the straight the same way they used to I will be writing a big check. The SIR is not a magic bullett it is another tool to put cars together that otherwise may not fit. As stated before the E36 is that car and the choices i could see were kick it out, move all the other ITS cars to ITA and we know crap flows down hill so I guess the 510's and rabbits wouldhave to disappear. Or use technology to work it out. I am impressed with Mr. Lytles attitude and I would offer any help I could give via the phone to help his development but I think if people are realistic they will add this unit in front of the maf snap a cone filter to the end of it and go to the dyno. I would then lay the dyno sheets side by side and I think you will see the computer compensates up to the point the engine runs out of air. I made that offer in one of these threads that anyone that want to go to the dyno for a half day that I would go along and help to tune or what ever I can offer at the dyno. I charge 75 bucks an hour shop rate for my time and I would donate that to prove this works. Now any of you eastcoasters would have to cover airfare also..
I'm just trying to figure out if everyone thinks bmw 325's make 225 rwhp? That number is absurd. At the figures you provided they would be running 281 hp @ the crank!
I think we will have to manage without you.......because there is no way in hell I'm flying you in! hehe
Marshall's attitude is pretty much the same as mine, he is just more diplomatic.
We'll keep you abreast of the SIR experiment and thanks for RC Eng. link, mine are going out next week to them.
[snapback]72522[/snapback]
[/quote]I'm just trying to figure out if everyone thinks bmw 325's make 225 rwhp? That number is absurd. At the figures you provided they would be running 281 hp @ the crank!
I think we will have to manage without you.......because there is no way in hell I'm flying you in! hehe
Marshall's attitude is pretty much the same as mine, he is just more diplomatic.
We'll keep you abreast of the SIR experiment and thanks for RC Eng. link, mine are going out next week to them.
I occurs to me - late in the game, obviously - that nobody has really explained HOW an SIR is supposed to work.
Power output is proportional to airflow thorugh an engine - pretty damned directly - so if airflow in can be controlled, so can power.
Air is a fluid and behaves in very predictable ways when it flows, until it reaches the speed of sound (the "sonic" thing referred to above), at which point it starts behaving VERY differently. This killed all of those test pilots before Chuck Yeager and the X1 finally got trans-sonic (going to and past the speed of sound) airflow under control, and broke the sound barrier.
It is relatively easy (and repeatable!) math to figure out (1) what kind of airflow corresponds to what kind of power, and (2) at what cross-section of inlet that volume of air is forced to "go sonic." The point at which it does, airflow goes all junk and the engine stops making power.
Yes - this technology has been used in other series, pioneered in Euro/Asian/Brit F3 20 years or more ago. My concerns, fustercluck-wise, are less about the technical aspects of implementing SIRs in club racing, and more about the policy implications. It's not going to be long, regardless of how well this answer plays out in ITS on one make of car, before someone seriously suggests that in lieu of a set of rules defining modifications, we implement IT28, IT25, IT23, and IT21 - with each class governed by an air hole and Katie-bar-the-door on the engine rules under that restriction.
WHY would this be a problem? For precisely the same reason that F3 engines cost a bazillion dollars to develop, and WRC engines face the same problem, constrained by boost limit: It all comes back to maximizing the area under the torque curve and those little changes can in fact become meaningful, to a race-winning degree.
K
Power output is proportional to airflow thorugh an engine - pretty damned directly - so if airflow in can be controlled, so can power.
Air is a fluid and behaves in very predictable ways when it flows, until it reaches the speed of sound (the "sonic" thing referred to above), at which point it starts behaving VERY differently. This killed all of those test pilots before Chuck Yeager and the X1 finally got trans-sonic (going to and past the speed of sound) airflow under control, and broke the sound barrier.
It is relatively easy (and repeatable!) math to figure out (1) what kind of airflow corresponds to what kind of power, and (2) at what cross-section of inlet that volume of air is forced to "go sonic." The point at which it does, airflow goes all junk and the engine stops making power.
Yes - this technology has been used in other series, pioneered in Euro/Asian/Brit F3 20 years or more ago. My concerns, fustercluck-wise, are less about the technical aspects of implementing SIRs in club racing, and more about the policy implications. It's not going to be long, regardless of how well this answer plays out in ITS on one make of car, before someone seriously suggests that in lieu of a set of rules defining modifications, we implement IT28, IT25, IT23, and IT21 - with each class governed by an air hole and Katie-bar-the-door on the engine rules under that restriction.
WHY would this be a problem? For precisely the same reason that F3 engines cost a bazillion dollars to develop, and WRC engines face the same problem, constrained by boost limit: It all comes back to maximizing the area under the torque curve and those little changes can in fact become meaningful, to a race-winning degree.
K