How dyno numbers are utilized by ITAC

[Andy Bettencourt]

If I remember correctly, the ITS E36 motor was a 2.5 single vanos on the intake cam. CB

I think the conversation is specfic to the E46 versions.

[JeffYoung]

Maybe Steve E. can weigh in on the Irish Mike ITS E46 car. I vaguely remember it, but I think he converted it to an ITR car after a year or two. I don't remember it (the ITS version) running away from the field at Roebling though.

[Chip42]

in 2008 the then ITS 323 was leading the SIC over MVS when he spun entering 4. MVS went on to win in his miata (Andrew C won ITA in another ISC miata). I think the following year Irish Mike went to ITR with that car.

it wasn't a slouch but I would have expected it to pull a miata harder in a strait line. no doubt Irish Mike had it tuned as close to perfect as he could, so it's safe to call it a 9/10ths car, minimum. I remember his justification (to me, when I asked) for going to ITR that the 323 was too slow. I'm sure the actual response was much more colorful.

[JeffYoung]

As you know, that's a Miata track. I've seen the ITS ISC Miatas lose exactly once there -- to John Williams' 240z. I thought John still had the ITS track record, but looks like Mike has it now (still all very close).

Hard to gauge that track by times though, it is so temp dependent.

in 2008 the then ITS 323 was leading the SIC over MVS when he spun entering 4. MVS went on to win in his miata (Andrew C won ITA in another ISC miata). I think the following year Irish Mike went to ITR with that car.

it wasn't a slouch but I would have expected it to pull a miata harder. no doubt Irish Mike had it tuned as close to perfect as he could, so it's safe to call it a 9/10ths car, minimum. I remember his justification (to me, when I asked) for going to ITR that the 323 was too slow. I'm sure the actual response was much more colorful.

[quadzjr]

I was at that race between Irish Mike, MVS, and the ITR red BMW Z. that was an intense race. I believe they were constantly in 19's (could be wrong, but I remember they were on pace with our FP times that was inthe 18's.) For what it is worth the faster setup of the MVS ITA Miata (better splitter and new motor, and pre-roll at driver school) With Andrew C driving was about 1-2 seconds a lap slower than the ITS cars mentinoed.

so mathmatically

ITS BMW > ITS Miata (at miata track) at sebring Irish mike won.
Both ITS > quick ITA miata with good driver
quick ITA miata > ITA miata at last race at RRR
ITA miata at last RRR race>ITS TR-8

[JeffYoung]

John Carter drives that ITA ISC Miata very well. He's not lacking for power at all though. He could stay in my draft at Roebling. The one place on the track -- the front straight -- where I should be able to put some distance on him, I could not. The rest of it, that's Miata heaven. ITA Miatas have won the overall there several times. I was lucky to beat him once back in April and thought I had him on Sunday in July, but he made a great pass on me in 1.

I don't think an S car has officially been in the 19s at Roebling. Track record is 20.5 (Irish Mike) and I think Charbonneau and Williams have been in the 20s. Best I've done is a high 21.

[quadzjr]

John Carter drives that ITA ISC Miata very well. He's not lacking for power at all though. He could stay in my draft at Roebling. The one place on the track -- the front straight -- where I should be able to put some distance on him, I could not. The rest of it, that's Miata heaven. ITA Miatas have won the overall there several times. I was lucky to beat him once back in April and thought I had him on Sunday in July, but he made a great pass on me in 1.

I don't think an S car has officially been in the 19s at Roebling. Track record is 20.5 (Irish Mike) and I think Charbonneau and Williams have been in the 20s. Best I've done is a high 21.

Not saying that John doesn't drive the heck out of the car. That car has had some rough times. (it was rolled at the double school last year). It has a good motor, MVS puts out a good product. My point is that Mike in the BMW on a miata track was toe to toe with the best in ITS miata. Both with great drivers.

[JeffYoung]

John's car has a VERY good motor.

I am certainly not saying I'm among the best ITS cars to run at Roebling. I'm definitely one rung (at least) below Irish Mike, and Andrew, and Mike and Kip, and John Williams.

But I think I have enough time up front at the track, and in racing with the Miatas, to think that a well prepped, well driven ITS or ITA Miata is going to very, very hard to beat there. Can be done, certainly, but that track -- a big long momentum track - is perfect for that car.

The only place I have an advantage, or a Z car, is the last 1/3 of the front straight, and even there, Mike at ISC has done so well with power development that this disadvantage seems to have disappeared.

Just confirms that there is always development to be done.

[quadzjr]

John's car has a VERY good motor.

I know it has a good motor.. it is the same car/motor Andrew C. drove during the SIC race that was mentioned before. That he (Andrew) was running around significnatly faster per lap faster a few years agoan what John was doing at the last race at RRR acording to MVS while he was timing john during qualifying sessions. Although htis last weekend the track was fairly greasy IMHO.

Actually during the last race they did adjust the tune on the computer to help resolve some lean conditions they were having. Seemed to work as the plugs looked good when he came in during the middle of the saturday qualifying event.

[JeffYoung]

As you know, that track is very temp dependent.

In qual in the morning you basically got (in my car anyway) one or two laps before you couldn't get grip in 8/9, which as you also know kills your lap times.

FWIW, I think John's times in the 22 would be up there with Charbonneau's in the fall.

FWIW again, where John "beats" ITS cars is in two places. Turn 6 and 8/9. He's on the gas way earlier than us in 6, and then flat through 8/9.

I could pull him in 3, and some on the front straight if he was not right in my draft. 4/5 was a wash, as was 1/2.

[quadzjr]

Watching all of the miata that drive for MVS they have the mojo. They all seem to take the same lines and they are fast. I have seen the traqmate data for the cars and it is impressive. My favorite is the 5-6 area.. Flat... slight lift.. flat again.. I have tried to do that in my car.. not a chance.

but for the original question, Atleast one BMW in ITS was fast against a fast ITS miata at a miata track. Who knows what was done, to the car and what prep level? You can always ask Irish Mike, he is a pretty cool guy. Dan might know as well?

[gran racing]

When using drive train loss percentages to estimate flywheel HP from dyno numbers, does that percentage decrease the higher the cars HP is?

For example, we dynoed a 348 HP RWD car today. Should we use 18% to get close to the flywheel number? What if the car was only 150 HP (still RWD)?

[erlrich]

When using drive train loss percentages to estimate flywheel HP from dyno numbers, does that percentage decrease the higher the cars HP is?

For example, we dynoed a 348 HP RWD car today. Should we use 18% to get close to the flywheel number? What if the car was only 150 HP (still RWD)?

The more I think about it, the more I think that is a really good question. Why in fact do we use a % for drivetrain loss instead of a constant value? Does a 300 HP (crank) RWD car actually require 18 more HP to turn its drivetrain than a 200 HP RWD car?

[gpeluso]

I understand that a dyno produces only a number that can be manipulated....but wouldn't it be a great idea for a region sometimes to have a dyno available to put top runners on to see comparables of that time and day....still a number...but should be relative to each other. Now this should not be used to dq anyone but it sure would make people think that something is going on with THAT car or an adjustment is in order from the powers to be.....might help honesty? or just scare people into honesty. What I read about what Greg Amy did with that whistler was a neat idea that was not used to dq people at all.... just informational purposes and it sounded like it worked.

Greg

[JeffYoung]

This is a good question. I had this discussion with someone not long ago actually.

You would think the loss stays constant but at least two other factors to consider:

1. There is some legitimate literature out there suggesting it does not. As hp increases, you get more losses in the tranny, etc. I'll try to dig it up

2. Second, for IT purposes, remember we are dealing with "batches" of cars, grouped in 60-80 stock hp (ITC), 80 to 110 (IT, 110 to 140 (ITA), 140 to 190 (ITS) and 190 to 240 (ITR). This reduces the effect of the use of a percentage since it's not like we are comparing an 80 stock hp car to a 240 one.

[DavidM]

How dyno numbers are used to back-calc crank HP is the biggest issue I have with the process. A small change in one number can mean plus or minus 100 lbs for a car. We all know what sorts of debates have been had over 100 lbs.

David

[JeffYoung]

Yes, and it gets worse in the lower classes where 1 hp can be 20 lbs.

[Andy Bettencourt]

How dyno numbers are used to back-calc crank HP is the biggest issue I have with the process. A small change in one number can mean plus or minus 100 lbs for a car. We all know what sorts of debates have been had over 100 lbs.

David

That's why the ITAC has it's 'confidence vote' and requires much more than one dyno sheet from one source.

And as long as the drivetrain loss is applied consistently, that piece isn't a variable.