Andy Hollis' One Lap Miata (K24 Honda power)
#241
On the Miata with 225 Rival-S, I am cooking the rear tires after a few hard laps. Backing off brings them back, though. Saw the same thing at NCM on the west course (not full). These are both shorter courses with lots of turning Tracks with longer straights would likely provide more cooling. For example, I had no issues at COTA.
#242
Getting back to this...big stuff coming soon, but here's a snippet that will helps others doing this same swap...
The K-series MAP sensor is designed to fit in a hole that is pretty deep, sealing against an o-ring. If the metal is thin, the o-ring does not seal perfectly. The metal in the GE intake is relatively thin.
I had a problem start to surface recently at COTA when the car began running super rich during the last session. I limped it home and eventually discovered MAP readings that were a little lower (less vacuum) than I had been seeing. I fixed it by installing a second o-ring around the base of the sensor “stub” and using a washer on the bolt to match the o-ring height. This did two things: 1) it set the standard o-ring depth shorter, and 2) what the standard o-ring does not seal, the second one does. I also put some sealer on the bolt threads since that penetrates the manifold as well.
The K-series MAP sensor is designed to fit in a hole that is pretty deep, sealing against an o-ring. If the metal is thin, the o-ring does not seal perfectly. The metal in the GE intake is relatively thin.
I had a problem start to surface recently at COTA when the car began running super rich during the last session. I limped it home and eventually discovered MAP readings that were a little lower (less vacuum) than I had been seeing. I fixed it by installing a second o-ring around the base of the sensor “stub” and using a washer on the bolt to match the o-ring height. This did two things: 1) it set the standard o-ring depth shorter, and 2) what the standard o-ring does not seal, the second one does. I also put some sealer on the bolt threads since that penetrates the manifold as well.
#243
Happy New Year!!
Remember this?
Solution => We are fitting 285/30-18 Bridgestone RE-71R's on 11's by tubbing the inner fenders and using a wide-body kit from DG Motorsports (AWR source).
This is a new size for that tire, due 3/1. In the meantime, we'll use 255/40-17 on 10's.
Proof of concept comes from the Wootton SSM autocrosser seen below in black using the same flare kit around 285 Hoosiers in front, and 315's on 12 in the rear. Rules disallow tubbing for that car, so he makes up for the 25" diameter by jacking up the perch height an inch. He's local, so I have studied it carefully.
The white car (Steve Garnjobst's XP autocrosser) is an example of a no-rules solution with tubbed inners. Not pretty, but very functional. Allows the suspension to have the same travel as with the typical 23" tall tire. You'd still have the other 1" higher ride height from chassis to ground, so Steve also moved all of the suspension pick-up points up an inch to get that back too. We will not be going that far...at least at this point.
While I could do this myself, it's being farmed out to someone who can make it pretty...since this car will see some more Optima event exposure in 2016. Apex Auto Works in Houston will do the fab. They do great race car construction, as well as paint and body...and vinyl is what they originally cut their teeth on. So we have many options on final finish. They have obtained a donor chassis (seen here in red) to cut out inner fenders that will then be blended onto mine about an inch or so up. Should make it look much more stock appearing.
Glass parts are built and enroute. Car goes under the knife in a week, with the goal to display it the end of January at the GRM tent at the Rolex 24 in Daytona.
PS: For non-200tw events, you can imagine the possibilities of slicks that we can run with so much room for activities.
Remember this?
I'm having trouble getting all the power down even in 3rd gear coming off corners. 225 Rival-S on 9's can't handle 300hp in 3rd unless you are perfectly straight. And I am going through rear tires at a prodigious rate as a result. On r-comps, the solution would be a no-brainer...but One Lap rules say 200tw.
So...time to do "what they say can't be done".
So...time to do "what they say can't be done".
This is a new size for that tire, due 3/1. In the meantime, we'll use 255/40-17 on 10's.
Proof of concept comes from the Wootton SSM autocrosser seen below in black using the same flare kit around 285 Hoosiers in front, and 315's on 12 in the rear. Rules disallow tubbing for that car, so he makes up for the 25" diameter by jacking up the perch height an inch. He's local, so I have studied it carefully.
The white car (Steve Garnjobst's XP autocrosser) is an example of a no-rules solution with tubbed inners. Not pretty, but very functional. Allows the suspension to have the same travel as with the typical 23" tall tire. You'd still have the other 1" higher ride height from chassis to ground, so Steve also moved all of the suspension pick-up points up an inch to get that back too. We will not be going that far...at least at this point.
While I could do this myself, it's being farmed out to someone who can make it pretty...since this car will see some more Optima event exposure in 2016. Apex Auto Works in Houston will do the fab. They do great race car construction, as well as paint and body...and vinyl is what they originally cut their teeth on. So we have many options on final finish. They have obtained a donor chassis (seen here in red) to cut out inner fenders that will then be blended onto mine about an inch or so up. Should make it look much more stock appearing.
Glass parts are built and enroute. Car goes under the knife in a week, with the goal to display it the end of January at the GRM tent at the Rolex 24 in Daytona.
PS: For non-200tw events, you can imagine the possibilities of slicks that we can run with so much room for activities.
Last edited by AndyHollis; 01-01-2016 at 08:06 AM.
#245
Project Big Wheel has begun.
That moment when somebody takes a sawzall to your pride and joy...
After the tubbing and flares are complete, we'll be converting to a 5x114.3 pattern using this method: MiataV8 Conversion: Five Lug Conversion
That gets a better bearing in the front, and a super easy five-bolt hub swap in the rear. I'm also investigating a couple of other front hubs to reduce the machining effort, but the FD RX7/Probe/MX6 hub with sleeve is a good known quantity.
That decision was made when we weighed Wootton'scustom 4x100 CCW wheel and discovered it was 26 lbs. Instead, we'll be using an off-the-shelf Enkei RPF1 18x10.5 ET15 5x114.3 that weighs 19 lbs for half the price, and available with no waiting.
Meanwhile back at the ranch...Andrew Keisler is working on a five-lug version of his front drop spindles for me.
That moment when somebody takes a sawzall to your pride and joy...
After the tubbing and flares are complete, we'll be converting to a 5x114.3 pattern using this method: MiataV8 Conversion: Five Lug Conversion
That gets a better bearing in the front, and a super easy five-bolt hub swap in the rear. I'm also investigating a couple of other front hubs to reduce the machining effort, but the FD RX7/Probe/MX6 hub with sleeve is a good known quantity.
That decision was made when we weighed Wootton'scustom 4x100 CCW wheel and discovered it was 26 lbs. Instead, we'll be using an off-the-shelf Enkei RPF1 18x10.5 ET15 5x114.3 that weighs 19 lbs for half the price, and available with no waiting.
Meanwhile back at the ranch...Andrew Keisler is working on a five-lug version of his front drop spindles for me.
Last edited by AndyHollis; 01-12-2016 at 08:26 AM.
#246
Project Big Wheel has begun.
That moment when somebody takes a sawzall to your pride and joy...
After the tubbing and flares are complete, we'll be converting to a 5x114.3 pattern using this method: MiataV8 Conversion: Five Lug Conversion
That gets a better bearing in the front, and a super easy five-bolt hub swap in the rear. I'm also investigating a couple of other front hubs to reduce the machining effort, but the FD RX7/Probe/MX6 hub with sleeve is a good known quantity.
That decision was made when we weighed Wootton'scustom 4x100 CCW wheel and discovered it was 26 lbs. Instead, we'll be using an off-the-shelf Enkei RPF1 18x10.5 ET15 5x114.3 that weighs 19 lbs for half the price, and available with no waiting.
Meanwhile back at the ranch...Andrew Keisler is working on a five-lug version of his front drop spindles for me.
That moment when somebody takes a sawzall to your pride and joy...
After the tubbing and flares are complete, we'll be converting to a 5x114.3 pattern using this method: MiataV8 Conversion: Five Lug Conversion
That gets a better bearing in the front, and a super easy five-bolt hub swap in the rear. I'm also investigating a couple of other front hubs to reduce the machining effort, but the FD RX7/Probe/MX6 hub with sleeve is a good known quantity.
That decision was made when we weighed Wootton'scustom 4x100 CCW wheel and discovered it was 26 lbs. Instead, we'll be using an off-the-shelf Enkei RPF1 18x10.5 ET15 5x114.3 that weighs 19 lbs for half the price, and available with no waiting.
Meanwhile back at the ranch...Andrew Keisler is working on a five-lug version of his front drop spindles for me.
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Home of the original KMiata Swap
K24 NC swap is coming in 2024! Learn more
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#257
One Lap uses a 200tw restriction as one of its few rules. You also have to finish the entire event on one set of tires...with 2/32nds remaining.
The fastest 200tw tires right now for a 3-lap time trial are the Rival-S and the RE-71R. The former comes in a 225/45-15, but not the latter. Further, the Rival-S is not good in deep water, whereas the RE-71R is amazing (see my GRM deep water testing sidebar in the track test article).
So ultimately, I wanted to find a way to run the RE-71R in sufficiently large enough size to put all the power down in 3rd, and with enough meat to not wear out during the week. 255/35-18 (or 255/40-17) would probably be enough, but with just a little more effort, I can also fit the new 285/30-18. Both are close to 25" tall and require massive fender work. I have the 255's on the way now and will compare them to the 285 once those are released. I'll run whichever is faster.
Last edited by AndyHollis; 01-14-2016 at 10:22 PM.
#258
They just have the R&D and history that Mazda doesn't. The MZR/L series is undeniably a good motor, especially the DISI; however, the K series motor is a contemporary equivalent, and it's just heads and shoulders above Mazda's powerplant efforts.
#259
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This project is awesome, and i'm sure the grip will be amazing. But damn, 18's look ugly as sin on a miata.
Personal preference.
I would still rock them for the grip
Also in for handling feedback, as historically heavier wheels means a worse ride/handling.
Personal preference.
I would still rock them for the grip
Also in for handling feedback, as historically heavier wheels means a worse ride/handling.
#260
I mentioned it a bunch on mnet when everyone was whining about "y only 155hp! honda makes 200hp out of 2 litre!!", but it's worth repeating that Honda's the largest engine manufacturer in the world, had an F1 team and is getting back into developing F1 motors, and has a massive motorcycle business with the history to go with it, as well. Not to forget that Honda is one of the larger auto manufacturers and Mazda is comparatively quite small (and fragile when they keep betting the farm on the rotary).
Of course, the "right" answer is the infinitely variable BMW Valvetronic.
But we're getting a little off-topic now...