Power Needed for Sub-2min Thunderhill Lap? - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-16-2012, 09:31 PM   #21
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Originally Posted by nitrodann View Post
Im not sure as you havent actually said how much experience you have at the track, or this on in particular, but id say you have a year of track days ahead of you before you are close to the cars limit on that track.

And yes it does take 100rwhp more to drop 3 seconds.

Dann
We'll just have to agree to disagree on the 100hp effect. I would bet heavily that I can get more than 3 seconds by adding 100hp. That's double the existing power. At Thunderhill, 3 seconds is only 0.2 seconds per corner exit.

Yes, I should have put something about my driving history in the OP. I've been instructing for almost 12 years now. Been to Thunderhill every year 6-8 events (Hooked on Driving, TEAM Racing, NCRC). For about the last 7 years, I have been doing between 35 and 50 track days per year as an instructor and driver. Other tracks attended include Buttonwillow a dozen days, Reno-Fernley (Lots!), Sears a dozen days, Laguna a couple of times, and Miller Motorsports Park 6 days. I estimate the total at somewhere around 400 days.

Luckily, I've had some experience instructing in Miatas, but this is the first one I've owned and this is just the start of my second season. I should have reserved the last session for a solo run, but a 16.2 with a passenger is probably a 14.5 without. I'll post that video.

Adding the coil-overs gave me a huge gain. I think what I have to learn to drive is the effect of the new coil-overs on tire grip, which I'm pretty sure will only take me another a day. What an amazing difference! Really hope to see a 13.5 next time. Pretty sure I'll be within a second of max on the current setup, at that point.

I'm in the habit of not threshold-braking, though. I paid for two flat-spotted tires last year...didn't like that!! I'll have to push the braking zone harder to get the last full second.

Last edited by Builder; 02-17-2012 at 11:30 AM.
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Old 02-16-2012, 09:39 PM   #22
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Welcome, Builder. Check out the Miata Gallery and post up some pics!
Thanks, Brain! I will do that.
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Old 02-16-2012, 10:02 PM   #23
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I'm in the habit of not threshold-braking, though. I paid for two flat-spotted tires last year...didn't like that!! I'll have to push the braking zone harder to get the last full second.
This is a problem that will definitely affect your lap times. Learn to threshold brake and react quickly if a wheel begins to lock. With experience you can definitely notice a wheel beginning to lock and catch it before it's too late.
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Old 02-16-2012, 10:17 PM   #24
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Maybe closer to 2:10 through the bypass (bypass is worth ~2.0 seconds). A top SM is about 250lbs lighter and has another 10-15whp, and they will typically set pole at a regional SCCA race in the 2:07-2:08 range going over the top of 5 (so ~2:05-2:06 through the bypass). I would expect the weight loss to find ~2 seconds, and then power to find another 2+ seconds.
That sounds a little more like it. We're still a couple of seconds apart on theory, but, I learned a long time ago that perception isn't always reality and surprise myself.

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Up to around 140whp or so, there are major gains to be had in power, like a second for every 10whp you add. At a certain point, the gains diminish, though - if your car as it sits today (2500+lbs) is capable of a 2:10 through the bypass, a 140whp version might be capable of a 2:06 or a 2:07, but a 200whp version would only get to a 2:04 or so. That's why it would be 250+whp to get down to the 2:00 range.
Yup, that's all logical. Okay, that will probably be third or fourth-year benchmark. It will be fun trying to get there with 180whp!

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A little more than normal, yes - it was scorching hot that day, 95*F at least, and Thunderhill does not cope well with heat. Theseus has 350whp, ~300wtq, and a comp weight of under 2200lbs with driver, so it's not a particularly easy car to drive under any circumstance
Sweet! Yeah, hot isn't great for grip or performance. Just out of curiosity, how many hours will you run that engine before freshening?
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Old 02-16-2012, 10:38 PM   #25
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This is a problem that will definitely affect your lap times. Learn to threshold brake and react quickly if a wheel begins to lock. With experience you can definitely notice a wheel beginning to lock and catch it before it's too late.
Yeah, I know...I know. I can concentrate on that next time and weed it out of my driving style pretty quickly, I think...especially now that I have some serious grip available to actually use.

Man, those coil-overs made such a huge difference. Last session, I may have found the true extent of the XP8 pads. No fade, but peddle pressure a lot higher and the tires still held! Speed at the apex of turn-1 in the last session was 5 mph higher compared to the first. Got to love that! Really can't wait til next time to work on braking and entry. I still loose 1 mph turning through 8, even though WOT from 6 to 9.
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Old 02-16-2012, 10:53 PM   #26
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MS is MegaSquirt, a standalone ecu (completely replaces stock ecu). You'll need a wide band too, but it can save you some weight in the engine bay, and give you some power if tuned properly.

Your car is heavy. Consider ditching the power steering, air conditioning, charcoal canister, carpet, soft top, spare tire, jack, etc. try searching light weight miata on google, there's a good write up with a list of stuff to take out and how much it weighs.
Oh, yes. I've read a little about MS. That might be a little beyond my capabilities and time available to learn. Do you still have to build those boards and boxes and stuff? Will OBDII still work for smog?

Thanks for the pointer on weight. The Miata will start a diet immediately. Air conditioning? Really? Yeah, that' heavy. Dang, not sure I want to do without that!
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Old 02-16-2012, 11:08 PM   #27
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100whp in the OP's car would be worth about 7s assuming the car is set up halfway decent.

lbs/hp required is a sliding scale, as gross weight goes up a lower lbs/hp is required for the same lap time. A lighter car stops and turns harder.

A typical lightened HPDE Miata can get down to 2200# with driver and a splash of fuel with spending big bucks. Said 2200# car with an EP style air dam, small duck tail spoiler, 225/45 medium compound tires (R6,NT01,C51 Z214,R888,RA1)
and about 170whp would go under 2:00 in the right weather.

160whp can be had with a stock bottom end, BP5A cam in BP4W or/ VVT head, P&P head, square top, I/H/E and ECU on pump gas. Add 10.5:1 or 11.0:1 pistons and you're above 170whp.
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Old 02-16-2012, 11:13 PM   #28
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When I pulled the a/c and p/s off of my '97 (with all the block brackets) I weighed it at 36lbs, nearly all of it at the very front of the car.

I also suspect if you're going to get to the lap times you want you might be in for a coilover upgrade as well.
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Old 02-17-2012, 12:30 AM   #29
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Originally Posted by emilio700 View Post
100whp in the OP's car would be worth about 7s assuming the car is set up halfway decent.
That's more along the lines of what I was thinking. I knew it would be a stretch to get from the current 2:15 to sub-2 with a 180whp kit. But, I figured I could get close. If I get that installed, a good goal will be 2:05.

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lbs/hp required is a sliding scale, as gross weight goes up a lower lbs/hp is required for the same lap time. A lighter car stops and turns harder.
Having driven probably 75 or 100 different cars on different tracks, from my 4,450# Impala SS to Ariel Atoms, that is exactly how I would state it. Well put, Emilio.

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Originally Posted by emilio700 View Post
A typical lightened HPDE Miata can get down to 2200# with driver and a splash of fuel with spending big bucks. Said 2200# car with an EP style air dam, small duck tail spoiler, 225/45 medium compound tires (R6,NT01,C51 Z214,R888,RA1)
and about 170whp would go under 2:00 in the right weather.

160whp can be had with a stock bottom end, BP5A cam in BP4W or/ VVT head, P&P head, square top, I/H/E and ECU on pump gas. Add 10.5:1 or 11.0:1 pistons and you're above 170whp.
Good stuff. When you say "160whp can be had with a stock bottom end", you don't mean that 160 is all it will hold, though, right? Those numbers are referring only to naturally aspirated?

What are the big-buck items to lower weight? CF parts, A-arms and clutch come to mind immediately.

I don't know what all those initials are for parts and stuff, but will find out.
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Old 02-17-2012, 12:52 AM   #30
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When I pulled the a/c and p/s off of my '97 (with all the block brackets) I weighed it at 36lbs, nearly all of it at the very front of the car.

I also suspect if you're going to get to the lap times you want you might be in for a coilover upgrade as well.
Thought it might be a few more pounds than that. All adds up and every little bit helps. What does your car weigh?

Coil-over upgrade? Yeah, probably. I just put the Megans in last week, so they will be around for a while. HUGE improvement over the original stuff with 123k miles on them. Maybe 2013. Next step will be top drawer.
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Old 02-17-2012, 01:03 AM   #31
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Here ya go:
http://www.lightweightmiata.com/beast/
As I said earlier, the biggest stuff is AC, PS, passenger seat, jack/spare, soft top, airbag(momo wheel?), carpet.
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Old 02-17-2012, 01:09 AM   #32
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Megans isn't really a good track setup.
Not sure why you can't get weight down to 2,400LB. I can do that without trying. Especially without the 100lb cage
145whp, 2270lb and 205 nt01 will get you to 2:02s. So 180whp and 225 will get you to 1:59.99. Adding 200lb add about 2 seconds.

Last edited by bellwilliam; 02-17-2012 at 01:31 AM.
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Old 02-17-2012, 01:30 AM   #33
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Originally Posted by curly View Post
Here ya go:
http://www.lightweightmiata.com/beast/
As I said earlier, the biggest stuff is AC, PS, passenger seat, jack/spare, soft top, airbag(momo wheel?), carpet.
What a great list! Thanks, Curly. Wow, the site owner has way more patience than I for details. Brilliant!
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Old 02-17-2012, 01:44 AM   #34
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Megans isn't really a good track setup.
Compared to many coil-overs, probably not. However, they are orders of magnitude better than what I had.

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Not sure why you can't get weight down to 2,400LB. I can do that without trying. Especially without the 100lb cage
Haven't tried yet, but sounds very doable.

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Originally Posted by bellwilliam View Post
145whp, 2270lb and 205 nt01 will get you to 2:02s. So 180whp and 225 will get you to 1:59.99. Adding 200lb add about 2 seconds.
So, slightly more power, slightly more weight, and a slightly wider tire should be right there. You are making me drool for the sub-2 mark.

I read all the Thunderhill lap posts in the "Lap TImes" sticky at Miata.net. It would be great to see if that's possible. Gotta try it!
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Old 02-17-2012, 01:59 AM   #35
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Sweet! Yeah, hot isn't great for grip or performance. Just out of curiosity, how many hours will you run that engine before freshening?
The ACL bearings have a nickel layer that begins to deposit into the oil when the bearings are worn out, so I do regular UOAs and I'll pull the motor to refresh it when I see the nickel content spike in the oil. I would expect this to happen at around 60hrs of run-time.
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Old 02-17-2012, 03:05 AM   #36
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Originally Posted by Builder View Post
..
Good stuff. When you say "160whp can be had with a stock bottom end", you don't mean that 160 is all it will hold, though, right? Those numbers are referring only to naturally aspirated?

What are the big-buck items to lower weight? CF parts, A-arms and clutch come to mind immediately.

I don't know what all those initials are for parts and stuff, but will find out.
Stock bottom end will survive much higher power levels but that's not the point. The point is $$. You will not be required to spend a dime on the bottom end if it is a healthy NB2 (01-05) and your goal is 150-160whp.

Did I miss something or did you state budget constraints? Any questions about setting up a car must have that metric. Vast ocean of prep differences between a $4k and $40k HPDE car.
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Old 02-17-2012, 05:50 AM   #37
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Originally Posted by nitrodann View Post
Im not sure as you havent actually said how much experience you have at the track, or this on in particular, but id say you have a year of track days ahead of you before you are close to the cars limit on that track.

And yes it does take 100rwhp more to drop 3 seconds.

Dann
Ill apologise for this statement, its very vague.

In Australia not many tracks are longer than 1:45.

And my local is 1:10 in my aspirated NA6, top speed 90mph.
So an extra 100rwhp is only worth 3 seconds there, where as on a track thats over 2 mins long, and higher average speed (therefor wind drag) 7 seconds sounds right.

Dann
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Old 02-17-2012, 09:59 AM   #38
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The ACL bearings have a nickel layer that begins to deposit into the oil when the bearings are worn out, so I do regular UOAs and I'll pull the motor to refresh it when I see the nickel content spike in the oil. I would expect this to happen at around 60hrs of run-time.
Ahhh, that's how you save your engine. Didn't know how best to monitor the condition of a race setup. On a refresh, as long as there were no issues, what components do you always replace? Are there parts to machine with every refresh? Can you share a range on cost? Trying to get an idea on budget for a serious build.

By the way, awesome sound track in that video.
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Old 02-17-2012, 11:23 AM   #39
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Stock bottom end will survive much higher power levels but that's not the point. The point is $$. You will not be required to spend a dime on the bottom end if it is a healthy NB2 (01-05) and your goal is 150-160whp.

Did I miss something or did you state budget constraints? Any questions about setting up a car must have that metric. Vast ocean of prep differences between a $4k and $40k HPDE car.
LoL, yeah well... Mine is a '97 with 123k miles on it. That's the NB(1) engine? I added a spreadsheet of current costs to the "Details" page in my sig. I've spent $9k, including the car.

Didn't state a budget, but that I'm considering the VooDooII kit for $3,400. I'm budgeting $4k to go up a power level (turbo or supercharger and body changes for cooling, add the Sport Brake brackets to the rear (already have fronts), and keep my eyes open for a 6-speed and/or engine block for future upgrades. I'm spending some car budget on two other vehicles, as well, right now. Got to finish those (new engines) before I can go big on the Miata.

I haven't decided the VD-II is what I want yet, as I suspect there's a good package I can assemble from parts and the knowledge that folks share on this forum. The designed package is an easy and fast way to get everything needed, which has its benefits 'cause I don't know much (anything) about turbo systems. I also want to look at superchargers, as driveability is really important at the edge of control.

All that said, I'm very much in the learning stage on this and open to all options. Maybe it makes more sense to build a $3,400 N/A engine, if it will make a dependable 180whp. I don't have the time budget to do constant rebuilds and I can shift a stock engine all day long at 7k without any concerns.
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Old 02-17-2012, 11:37 AM   #40
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Ill apologise for this statement, its very vague.

In Australia not many tracks are longer than 1:45.

And my local is 1:10 in my aspirated NA6, top speed 90mph.
So an extra 100rwhp is only worth 3 seconds there, where as on a track thats over 2 mins long, and higher average speed (therefor wind drag) 7 seconds sounds right.

Dann
Now worries, mate! Yeah, Thunderhill is ~3 miles and the front straight allows my Miata to hit 101.xx MPH (10Hz GPS, 105 indicated) with this driver's last turn (15) exit speed.

Edited to say, there are some true race-prep cars that are capable of turning Thunderhill laps at 1:45.
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