Just trying to get a feel as to where my car should be running to have a fighting chance. I got it upto 105 today before it would really go anymore :/ number 2 cylinder has weak compression from what i was told when i bought the car.

Never had the cajones to take it over 120, but it got there no problem. Tires were screaming though ... (rated to 90mph)

never could get my zx2 up that high before it died, only cause of the govenor, but the mx3 just wouldnt go faster than 105. :/ i need to rebuild the motor on it so i can fix that compression problem.

106 for me until the govenor kicked in. i have been in a car that was doing 130+ but not driving... my tires are rated 160+ so i feel somewhat safe going that fast lol

I think just to prove a point to a civic(mid 80s horrible, fart can, ugly scoop, etc) I took it to 125 and backed off and slowed to 75 about a minute afterwords he comes flying up...yea it was pathetic.

I have s/r gauges if anyone was wondering how I knew it was 125

I was in a GSX that was at 145 had the speedo pegged and I know we were going faster than that. Fastest I ever took my Talon to was about 135-140.

i have takin mine to 110 easily, and then slowed cause i had an admin's younger sib in the car. but then again that was when my car worked. now it only goes to 70, and thats down hill.

i have the top speed on teamzx2 with 145 i would have reached 150 if i had a different clutch and flywheel, i think.

Josh a guy in texas pegged his s/r speedo and went well past 150...Just a heads up

I forget his name on teamzx2 but he was spraying. 200+whp dynoed

but josh is the only one to prove he went that fast for that thread topic...

and is there a theoretical limit to how fast our cars can go? i would think regardless of all the HP our trans would eventually no longer be able to accelerate the car any faster with 5th gear...

You can do the math for it.

The ZX2 has a .78:1 ratio for 5th gear, and 4.10:1 on the differential. Multiply the two together, and you get 3.198:1. Divide your engine's redline by that number (7000 / 3.198), and you get 2189 RPM max at the axles. Take your tire size (205mm), and multiply it by your sidewall height (55%), to get 112mm height on the radius of the tire. Times two to get diameter of the tires gives 224mm, and in inches that's 8.88" on top of the 15" rims we have. Total wheel diameter excluding elongation is 23.88". That, times PI is 75 inches per rotation, or 6.25 feet per rotation. At the above calculated 2189RPM, that gives 2189 * 6.25, or 13681 feet per minute. Multiply by 60 minutes per hour, gives you 820875 feet per hour. Now, simply divide by 5280 feet per mile.

The ZX2, stock 5spd, gears out at 155.46mph. It does not go faster without going past 7000 RPM or different gearing.

You can do the math yourself, if you know the gear ratios and RPM. It looks complicated, but it's really a bunch of easy steps. Just follow along, and change numbers out where you want to. You'll see that using the sedan ratios is a huge help for top-end, and will get the ZX2 well over 170mph.

Holy crap INSTA!!!! Lol I got my S/R up to 140 last night on I-70. Fun but stupid. O and got pulled over today for going 75 on Noland. but cop let me go cause i had my Quik Trip gear on for work.!!!!!!! I was really lucky but yeah you should be good at about 115-130 It really doesnt matter what top end speed you have just matters on how fast you get it there! GOOD LUCK!

Matt

lets just say it took about 3-4 miles to hit 105 :/

/wet blanket on/

Insta, what about aero drag? I'd agree if you're in a tailwind (a very fast tailwind.) If there isn't enough power to accelerate to 7000 rpm in 5th gear, you won't get to 155.

Unless your clutch is slipping, JDRZX2, I don't think the clutch matters, since it doesn't add/subtract power or change gearing.

And, speedos are notoriously inaccurate at higher speeds, and especially with different sized tires.

/wet blanket off/

Miata hits an indicated 100-105 at the end of the front straight at Heartland Park Topeka before braking for turn 1. (With convertible top down and windows down - adding hardtop for better aero is probably worth another 5 mph).

At Mid-America Motorplex, the end of the front straight is about 95-100 mph.

I've got 205/50-15 and the S/R gauge is run off 205/55-15 so it shouldn't be to far off in that respect. Eventually I get a higher speed than that with a turbo and I'll get an after market gauge to see how fast the car really goes. But that is a ways down the road and a couple thousand invested into the car.

I think the lightweight clutch and flywheel should allow the engine to turn faster, but mine is starting to slip a little. Nothing to not be expected out of stock components with 135k on them.

I didn't say it to start anything. The guy is fully built with spray. He has a vid of him pegging the speedo in a very very timely mannor. It was hosted on vits site. The guy is from texas.

And if a video isn't proof I dunno what is.

But yea I wasnt saying it to discredit anyone...just that the guy pegged his speedo like it was easy...cuz it was

I'd agree that the lighter weight clutch will accelerate faster. There might be a slight power-to-the-wheels advantage due to the lighter rotating mass - but I don't think it's very much.

I've had my s/r up to 145 with 17's and completely stock,matter of fact 3ppl we're in the car (including me) . I blew my first tranny that way, and it was video taped. I have not seen it since that night, my friend Nathan has the video in his safe.

with 205/50/15's at 150mph your really doing 140! do the math


Never done it again since.

That's why I run 205/55/15 ;)

there is a handy tire size/speed diff calculater on the internet somewhere. you enter your stock tire size and your new tire size and it will show you an outline of both so you can see how much bigger one is than the other and tell you how much to add or subtract from your speed to get a more accurate number...

@CJW- i was not trying to be mean or anything. Just that josh has the #1 spot cuz of his pic/vid whatever, i totally believe your friend got that fast, just the fact that he has not stepped up to prove it in that one particular post to oust josh...

@Insta- nice math, you come through as always! So your saying the trans will not be a limiting factor in top speed? that if the engine can rev higher and higher we can continue to accelerate? just making sure i am following this right

From what I have seen and heard, the G5M in a ZX2 will hold up to a lot of abuse. Jarred says the MX-3 guys are stripping gears at > 300whp, and as we all know, the differential is weak.

A top speed run is definitely something to try on the bottle or spooling, and for God's sake rent a runway or something to do it on.

roadtrip to the bonneville flats anyone? lol

well my main goal for now is to get this monster of a mtx swap done and out of the way so i can start gathering the rest of my turbo setup. once i am spooling i will begin to build a motor. this way i can counteract problems as i do swaps and installs without having to figure out which install the problem is coming from. if i did my mtx, turbo and motor install all at once, that would be a hell of a headache to sort out. this bumps my turbo ambitions up to around februrary sometime, with the motor following a few months later. maybe may'ish . fingers crossed my low mileage motor will last a few months running low boost tuned until i can swap motors...

Prolong the life of the motor by getting the thickest head gasket you can for it. It will lower compression. :)

im guessing you mean for the stock motor... that is a possibility. i only plan to run maybe 5 psi , 8 tops until the motor goes in.

@rodney- do you have any info on the heartland park circuit? such as how to go about getting to do some laps with your car and what safety equipment is needed? i would really like to give it a shot once i get some major hp going. i think it would be somewhat boring with the car as it is now...

Lets just assume you've got a "stock" alcohol/nitrous powered ZX2 in a pure vacuum :) It doesn't matter how inaccurate the speedo is, it's the speed that the little yellow lines (FROM THE AIRPORT RUNWAY) are zipping by. Arden asked about the theoritcal limit. If we can get 01CGNeon in here with his crazy fluid dynamics, we can find out how much drag the ZX2 might make, and if the motor at full tilt can overcome it.

I have the drag coefficent of the zx2 laying around here somewhere...let me see if I can find it.

And yes, I heard the 5th gear in the g5m's are weak, although I have a replacements for it :)

Road Warriors linky is what you're looking for. Need a decent helmet, just like autox, otherwise it's a safe street car. $45 to run three 15 - 20 minute sessions. Unfortunately, with the SCCA Runoffs coming up, there are no more open track events this fall, other than the Porsche Club or BMW club, and then you're up in the $150 - $250 range.

They might not like Josh's car with the cage - they may find that it's too close to a "Race car" for Road Warriors. He can try it, but it might be kicked out. I know of a Miata with a full cage and a FWD Dodge Omni Charger autox car with a full cage, and they wouldn't let either one run Road Warriors. Something about Insurance - probably mixing cage and non-cage cars together - but still seems like a crappy deal to me.

Another alternative is "High Speed Touring" series at Hallett Motor Racing Circuit west of Tulsa, OK (appx 5 hour drive from KC). $95 for several track sessions, with controlled passing.

oh wow really?!?! i had heard somewhere that i needed a roll cage to get on track plus fire equipment ect... basically be up to highest race car spec... well thanks for the info. i cant wait to get on track this spring.

when are the SCCA runoffs? i want to go

Autocross national championships are at HPT and start on Tuesday 9/26.

Runoffs races are 10/9 thru 10/15, with practice days beginning on 10/2. The SpecMiata race on Sunday the 15th (10:55 am) should be amazing.

i cant wait! i think i will go out there to check it out

Got mine up to 176 last year and 160 just the other day. Both times were on a closed course and only in 5th gear (still had one more gear to go).

However, in the Peon, the speedo only says 120 and I've buried that many times (usually followed by some sore of catastrophic failure... ).

What kinda courses do you know of that you can go that high? I want to see what my ZX2 caps out at.

Ummm... I'll have to get back to you on that one.

So it was a closed course by virtue of being dark out?

closed coarse as meaning he was only looking forward.

I'd like to top mine out also but only when I get a spare car, and 14's with proper tires on them. I'm pretty sure I'll get about the same results as last time, hoping minus the tranny boom.

I admit nothing.

so when you starting that post on your new motor project? .... tell all!

he already posted it. and im sure it doesnt take much of a straight to get a crotch rocket up that fast