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Need Faster Boost & rain tire info

Old 09-17-03, 07:15 PM
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Need Faster Boost & rain tire info

To all you hard core racers out there, help me out.

I have two questions.

What can we do to get even better response.

I have the sequential system, PFC tuned to 364 at the wheel and 4.88 gears in the rear.

I am looking for any advice on what we can do for faster spool up. Boost controllers? Waste gate work? what can we do?

Rain tires. I took 3rd at the Pro-Solo and it was dry, and 8th at the tour due to as you know the rain on Saturday. What do you racers use as rain tires. I am told the Hoosier dirt stockers do not work on our car due to the height. What can we do? I am hoping to find something as soft as the dirt stockers.

P.S. Congrats to Danny Pedrosa in his supercharged miata who trophed at nationals. Fastest Miata I have ever raced against.

Thanks for your help.

Allan
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Old 09-17-03, 08:02 PM
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Re: Need Faster Boost & rain tire info

Originally posted by Spank
Rain tires. What do you racers use as rain tires. I am told the Hoosier dirt stockers do not work on our car due to the height. What can we do? I am hoping to find something as soft as the dirt stockers.

With 15 inch wheels you could probably get a dirt stocker to fit, but they are only good for standing water, they'll chunk up and fall apart in merely damp conditions. So you'd also need an intermediate tire for wet but not flooded conditions.
I like full tread Kuhmos for the rain, the ones Dan Chadwick loaned you were shaved.
Rumor is that Hoosier is going to make a legal radial rain tire this year, but they said that last year too...so I'm not holding my breath

BTW...what happened to you at the banquet Friday night?
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Old 09-17-03, 11:58 PM
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With regard to faster boost response, yes a boost controller will give you substantially faster response. Basicly, a mechanical wastegate begins to open at some fraction of your final boost pressure, thus bleeding off exhaust energy you could otherwise be using. By switching to an electronic boost controller, the entire signal to the wastegate is blocked(allowing you to build boost faster), and then tiny amounts of exhaust are bled off to the wastegate in order to maintain the specified boost for longer than a mechanical wastegate could ever hold it. In short you make boost faster, and hold it much longer with an EBC. The best EBCs in my opinion are the HKS, Blitz, and Apexi AVCR. Each has its benefits, all are top rate. As for tires, you guys are out of my league. Congratulations to all that ran.
Regards, Carl Byck
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Old 09-18-03, 10:01 AM
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I agree w/ Carl a EBC will give slightly better boost responce than the stock FD system however a dedicated spring loaded ball valve based mechanical boost controler can be 99% as good, the real answer (and the HIGH $ one) is new BALL BEARING Turbos, not only do they spool UP faster but the don't spool DOWN as fast so they recover from quick on/off/on transitions (like up-shifts) MUCH faster than plain bearing turbos.
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Old 09-18-03, 10:02 AM
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Re: Re: Need Faster Boost & rain tire info

Originally posted by Rx7cat16
With 15 inch wheels you could probably get a dirt stocker to fit, ...
BUT 15" wheels won't fit over an FD's BRAKES
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Old 09-18-03, 10:29 AM
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Full tread V700's have very good wet grip and, IMO, the full tread Ecsta V700's have better wet grip. But, at full tread with the Ecstas, you have the infamous "groove of doom" problem ... then again, you just want them for rain tires, so it should be a good fit. Of course, that also means you need to get another set of monstrously wide wheels.

Faster spool .... Damian posted some interesting stuff with mechanical valves for pre-control and turbo control. Basically, flat boost response throughout the primary .... which would be very nice for auto-x. An EBC would work ... but I don't think it will be that substantially different in performance. Or, you could ditch the twins for a T3/T4 hybrid with a divided housing. Very quick spool and response ... just limited on top end. I've given this option some thought ... as I am also very weary of the excessive heat produced by the twins.
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Old 09-18-03, 01:38 PM
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How can a mechanical bleeder valve come close to an EBC? A mechanical valve is essentially another mechanical wastegate with the same downsides as the one you are already using. All you are doing is raising the threshold for the valve to open, but as with a mechanical wastegate, there is always some signal(exhaust energy) being bled off(wasted) once you reach the point at which the valve begins to open. If you want to test this(spool up, not ability to hold boost), and you have a mechanical valve, and a way to log the boost curve, here is what you do. Disconect the wastegate, and monitor the curve(this is the equivalent of an EBC), now do the same with your mechanical valve on line. the differnc in time between when you reach full boost is the benefit your particular set-up will realize with an EBC. If you are at or near maximum efficiency on your turbos(stock twins, and 364hp), the EBC will help you to hold boost longer because the maximum possible amount of exhaust energy is being utilized, not bled off into the atmosphere. Of course the amount of benefit to be gained will vary by set-up, but with entry level EBCs costing 150.00-200.00 used it seems crazy not to utilize the advantage, especially at the level of competition we are talking about. There is no way a mechanical valve will spool as fast, and there is no way it can hold boost as long, someone care to educate me otherwise?
Carl Byck

Last edited by in2twins; 09-18-03 at 01:51 PM.
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Old 09-18-03, 08:47 PM
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Re: Re: Need Faster Boost & rain tire info

Originally posted by Rx7cat16
With 15 inch wheels you could probably get a dirt stocker to fit, but they are only good for standing water, they'll chunk up and fall apart in merely damp conditions. So you'd also need an intermediate tire for wet but not flooded conditions.
I like full tread Kuhmos for the rain, the ones Dan Chadwick loaned you were shaved.
Rumor is that Hoosier is going to make a legal radial rain tire this year, but they said that last year too...so I'm not holding my breath

BTW...what happened to you at the banquet Friday night?
I should have known you would be here. I left Friday after the races to get home for a meeting Monday morning. You know how it is being competitive. Trophy position really only counts when you are 3rd or above. Below that whats the point? As you can tell I was very disapointed in my position. Charlie Shelton picked up my award I hope.

I hope to be faster next year. I have John Ames co-driving not this weekend but next. We will be driving Friday, Saturday and Sunday. I need to get faster and can use all the help I can get.

I really believe our cars should kick butt in this class. If they don't it's not because of the car it is us. Just like you said to me in Atwater. If I do not perform well I feel I have let our car down. Other people may think that is strange but you know what I mean.

Also how much does Eric want for his turbos? Do you notice any difference between your stock turbos and these?

Talk to ya later.

Allan
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Old 09-18-03, 08:49 PM
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Boost controllers

Thanks for the info, I will try the Blitz, I have heard great things about it.

Allan

Originally posted by Carl Byck
With regard to faster boost response, yes a boost controller will give you substantially faster response. Basicly, a mechanical wastegate begins to open at some fraction of your final boost pressure, thus bleeding off exhaust energy you could otherwise be using. By switching to an electronic boost controller, the entire signal to the wastegate is blocked(allowing you to build boost faster), and then tiny amounts of exhaust are bled off to the wastegate in order to maintain the specified boost for longer than a mechanical wastegate could ever hold it. In short you make boost faster, and hold it much longer with an EBC. The best EBCs in my opinion are the HKS, Blitz, and Apexi AVCR. Each has its benefits, all are top rate. As for tires, you guys are out of my league. Congratulations to all that ran.
Regards, Carl Byck
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Old 09-18-03, 08:56 PM
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Boost Controller

Great info Carl, that is the kind of stuff I need. As you can tell by my HP I have done everything you can in our class, and yes did the Flywheel last year.

Looking at doing the following for this next year.

Hood to help with heat and keep the intake cooler.
Would like to find a hood that I can use to feed the intakes directly and then modify for rain.

Blitz Boost controller.

Next for power will be new turbos. I have heard about the Garett ball bearing turbos and also have heard some about a small turbo. I am looking for as much boost and power by 2000-3000. I will call Japan if I have to and see what they do.

Allan


Originally posted by in2twins
How can a mechanical bleeder valve come close to an EBC? A mechanical valve is essentially another mechanical wastegate with the same downsides as the one you are already using. All you are doing is raising the threshold for the valve to open, but as with a mechanical wastegate, there is always some signal(exhaust energy) being bled off(wasted) once you reach the point at which the valve begins to open. If you want to test this(spool up, not ability to hold boost), and you have a mechanical valve, and a way to log the boost curve, here is what you do. Disconect the wastegate, and monitor the curve(this is the equivalent of an EBC), now do the same with your mechanical valve on line. the differnc in time between when you reach full boost is the benefit your particular set-up will realize with an EBC. If you are at or near maximum efficiency on your turbos(stock twins, and 364hp), the EBC will help you to hold boost longer because the maximum possible amount of exhaust energy is being utilized, not bled off into the atmosphere. Of course the amount of benefit to be gained will vary by set-up, but with entry level EBCs costing 150.00-200.00 used it seems crazy not to utilize the advantage, especially at the level of competition we are talking about. There is no way a mechanical valve will spool as fast, and there is no way it can hold boost as long, someone care to educate me otherwise?
Carl Byck
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Old 09-18-03, 10:22 PM
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Re: Re: Re: Need Faster Boost & rain tire info

Originally posted by Spank
I should have known you would be here. I left Friday after the races to get home for a meeting Monday morning. You know how it is being competitive. Trophy position really only counts when you are 3rd or above. Below that whats the point? As you can tell I was very disapointed in my position. Charlie Shelton picked up my award I hope.
Well, there are a lot of people who don't trophy at Nationals who would disagree with you on the 3rd and up thing... I wouldn't voice that opinion too loudly at national events
Yes, your trophy was picked up, I believe it was Cal that went up and got it.

I hope to be faster next year. I have John Ames co-driving not this weekend but next. We will be driving Friday, Saturday and Sunday. I need to get faster and can use all the help I can get.
I really believe our cars should kick butt in this class. If they don't it's not because of the car it is us. Just like you said to me in Atwater. If I do not perform well I feel I have let our car down. Other people may think that is strange but you know what I mean.
Putting John in your car should give you a really good idea of it's potential
At the moment I think that a well set up Rx7 with a good driver can kick butt in SM2, hard to say in the future, there is potential for quite a few other cars, especially the smaller ones that can get to the minimum weight...hopefully there will be some adjustments to that.

Also how much does Eric want for his turbos? Do you notice any difference between your stock turbos and these?.
Umm..._his_ turbos? You do know that the Rx7 is my car right Allen?
I'll have to let you know, depends on how long they stay in the car, which depends on how quickly the 3 rotor comes together.
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Old 09-18-03, 11:29 PM
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An EBC might not help, perhaps Apex'i already used good boost control logic in the Power FC. They do make pretty good boost controllers, so maybe they just took that and added it to the ECU.

Obviously you've had the car on the dyno a lot, but did you do a lot of tuning at the low RPM's you're worried about? Maybe fuel and ignition tuning will give you more bottom end and boost response. I believe the Power FC has an anti-lag function you can activate with the Datalogit software as well.

It's always been my understanding that regular EBC's struggle with the sequential system
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Old 09-19-03, 12:47 AM
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Tyson, you miss me, that's nice
Sequential is a problem for boost controllers which use "fuzzy logic" ie, they try and learn the boost pattern. The simple solution is not to use the learning feature on your EBC if you are in sequential mode, and have a EBC capable of learning boost patterns. Alternately use an EBC without fuzzy logic. The third solution is to switch to a non-sequential configuration so that both turbos spool simultaneously. The advantage is that boost response is linear, not stepped, and therfore easier to predict, and control, particularly if the second turbo hits at an rpm that you are often in during a turn, or transition. The transition from one turbo to two becomes more pronounced as you approach the maximum potential of the system. The downside is lag, two turbos will spool more slowly, in a Supra in sequential mode, the first turbo is always on line, the second turbo comes on at 4000 rpm, and once activated stays online unless you drop below 3500 rpm. This is easy to manage in stock form, as the transition is transparent, but at BPU(boost controller, and exhaust ~450hp)the hit from the second turbo is in the range of 150hp! Try getting a 150 shot just before you apex that critical part of the track, you can see why most road race, and AX Supras run non sequential . I'd guess the lack of torque off boost in an RX7 makes this the least desirable option for AX, but a good one for road racing. I'd get an EBC, and experiment with various configurations(sequential vs non) until you find one that suits your driving style, ultimately being one with the machine, regardless of its behavior will yield the fastest times. Thanks for listening, and as always, the above is IMHO. Carl Byck
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Old 09-19-03, 01:15 AM
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I thought we were talking autocross here.

Carl, I haven't missed you, I just haven't started shooting yet!!
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Old 09-19-03, 03:53 AM
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rain+fd=you had better love to drift or be a very good driver. even with S-03's or GP-D3, you'll spin. light car+high hp=hard to handle in the rain
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