My 200mph budget build

turbotoaster · 23 Jan 2010 at 00:19

spoke to jim at racing beat about his car and spent some time researching it, its running a triple rotary engine(20b) they did 242mph with 800bhp, they would have gone a lot faster but had some stability issues as your driving on salt and not tarmac, ie it still wants to wheelspin at over 200mph

here is the email i got back from them

'Your question was forwarded to Jim Mederer, Racing Beat's co-founder and chief engineer, for review. The following is his reply to your inquiry:

Our Bonneville FD had a custom chassis with no part of the stock chassis. I made the driveline tunnel quite large to allow heated air to pass through. The entire car had a carbon fiber underpan bonded to the chassis. I used a 4" thick radiator to restrict air volume while maintaining high speed cooling. Intercooling was done with ice and water to reduce drag. I urge you to use a 4" to 5" high spoiler lip to obtain down force at the rear - critical for traction and stability.

Jim Mederer'

this is there car by the way

for refence he hit 204.99mph in 1.3miles aswell on salt

turbotoaster · 23 Jan 2010 at 00:20

one thing i havent mentioned here aswell is that the car will be running pre-turbo water injection, im making my own kit aswell and it will be a purely mechanical system so no pumps involved, got this idea from a couple of guys in america doing it, one guy runs 23psi on pump fuel on a big turbo daily, the other runs 32psi on pump fuel and has 700bhp.

this design isnt mine but im using it to give you an idea how it works.

very simple set up, good thing is, the solenoid will open at say 1bar(depends what i set it at) and the more boost you are running, the more water, so theres no need to fiddle with jet sizes once you have set it up to flow the right amount of water

Ill be running around 2bar of boost pressure

turbotoaster · 23 Jan 2010 at 00:21

ok onto the deal with power, i did some gear testing yesterday to determine what needs to be done

So i went out with my gps meter to do some gear testing.

to do 100mph(gps) i need to do 4500rpm, give or take 20rpm

so to do 200mph i need to pull 9000rpm, simple maths. this is on 255/40/17s there maybe 1mph more for tyre expansion but ill leave that out to make it easier. also a 4.1 diff

So i got out my gear calculator program i have to put the numbers in to see how i can help.

online i have found that the 5th gear results are much longer than they should be, 0.719, which must be incorrect else id be doing a massive speed.

Anyway i adjusted my 5th gear till i got 100mph at 4500rpm with tyres stated earlier.

This gave me a 5 gear ratio of 0.820 or 22.15mph per 1000rpm.

Now according to what the guy with the stock port and same turbo as me did, his max power was at 8200rpm, because of my big streetport im calculating that my max power will probably be about 8500rpm.

So to do 200mph im going to be past my max power and its gonna be trailing off, not good really at that means ill have less power where i need it most.

At my maximum power ill only be doing 188mph, so well short of the mark, so lets change the diff to an auto one to see what we can do.

now this changes the speed at max power to 198mph, which is much better, very close to the mark.

Ill have to wait to see what my final max power/rpm will be but it least im making progress on gearing.

also say for example i only make max power at 8200rpm like the other guy did i can still hit 200mph with 8250mph if i change my rear tyres to 255/45/17

hope this clears up any potential confusion people have had in the past

One thing about power is if i made 1000bhp at 6k but only 500bhp at 9k and i need 9k to hit 200mph i wouldnt do it.

But if im making 1000bhp at 6k but 640bhp at 9k i would hit 200mph.

So i can make up with tyres but i may need more than 640bhp to hit my target, hence the aim of 700bhp at around 30psi.

A completely stock engine(ie built by a guy on the mazda production line)with my turbo did 709bhp at 33psi and runs 9sec quarter miles so the power is avaliable

that way if 200mph is past my peak power slightly then it still should be above 640bhp.

this was from Rod about his old engine which was 750bhp on gas and did 201.6mph at that power

'On my last engine Peak Power was below 7.5k but held on to about 7.7k. We pulled 8.2k so was well past peak Power. BUT we could not pull the longer gearing so this was the best compromise'

So at 200mph he wasnt putting out the power people think he has because hes gone past peak power

olv · 23 Jan 2010 at 00:30

Just don't do this

Sin_Chase · 23 Jan 2010 at 00:44

Surely building the car to get to 200MPH at its absolute peak is a futile expirment in which you have a finite amount of space to do it in?

That's all well and good if you can go for as long as you want and eventually top 200 but are you not going to need to go above and beyond what is neccessary to get there in your limited stretch?

I don't know enough about the physics or maths to be able to say for sure but that sounds right in my head!

mk1_salami · 23 Jan 2010 at 03:39

Cool project and I'll be looking at this with interest. When do you plan to complete the car and go for 200mph?

Also the cheapest way to 200mph is a Busa, Full system exhaust and Power commander :cool:

turbotoaster · 23 Jan 2010 at 03:49

Sin_Chase said:
Surely building the car to get to 200MPH at its absolute peak is a futile expirment in which you have a finite amount of space to do it in?

That's all well and good if you can go for as long as you want and eventually top 200 but are you not going to need to go above and beyond what is neccessary to get there in your limited stretch?

I don't know enough about the physics or maths to be able to say for sure but that sounds right in my head!

well yeh, give me the autobahn and i dont need 700bhp, ill probably be ok with about 550bhp.

Id imagine if we are going to compare to top speeds that manufacturers quote, ie on an oval then id say the car should do 215-220mph with the right gearing/tyres.

But this is the only place in britain you can officially time a top speed run, yes if i was allowed on an oval then id do it there but no one would let a nobody like me on there, hence the limited distance

MikeHunt79 · 23 Jan 2010 at 04:19

Nice work, that turbo is massive! :eek:

I did see a rather quick (blue) RX7 at a run what you brung drag racing event last year, I have no idea what power it was running but it did the quarter in less than 9 seconds from what I remember...

One thing, because the RX7 engine is pretty light this thing was almost wheeling off the line! :eek:

Are you going to add any ballast or anything like that or are you going to wait until you test it to see if it's a problem at all?

Flukester · 23 Jan 2010 at 07:16

Peter Diffey said:
For all out top speed, weight isnt an issue (just might take longer to get upto speed), it is all about drag forces and having enough power to overcome them untill you reach 200Mph.......

weight is also a issue.... you stand more chance with it being lighter surely ?

wez130 · 23 Jan 2010 at 09:56

very interesting read, look forward to see how this goes

cyclops12 · 23 Jan 2010 at 10:02

wez130 said:
very interesting read, look forward to see how this goes

Yes this

kaiowas · 23 Jan 2010 at 10:34

Slightly over budget but how about 200mph, decent all round performance (It won TSS in 2008, was runner up to an ex British rally champion in 2009) and subtle enough to leave it in Tescos car park without drawing any attention:

http://pistonheads.co.uk/sales/1441776.htm

stulid · 23 Jan 2010 at 10:39

All serious rx7 have a V mounted cooling system surely?

PlacidCasual · 23 Jan 2010 at 10:44

Not wishing to be awkward here but above approx 155mph cars need especially designed aero dynamics to maintain the down force on the car. I would question whether it is a simple matter to adjust a road car for such speeds. If you look at super cars they have venturi's in the body work and floor pan to accelerate the air creating low pressure.

Whilst you may be able to create a car with sufficient power and drag to reach the speed, doing it safely is another matter. I would strongly urge you before attempting this to get guidance from a specialist engineer, they may be able to suggest small changes which will immeasurably improve the safety.

ZG002 · 23 Jan 2010 at 10:48

PlacidCasual said:
Not wishing to be awkward here but above approx 155mph cars need especially designed aero dynamics to maintain the down force on the car. I would question whether it is a simple matter to adjust a road car for such speeds. If you look at super cars they have venturi's in the body work and floor pan to accelerate the air creating low pressure.

Whilst you may be able to create a car with sufficient power and drag to reach the speed, doing it safely is another matter. I would strongly urge you before attempting this to get guidance from a specialist engineer, they may be able to suggest small changes which will immeasurably improve the safety.

Plenty high powered Skyline's etc out there that will crack 200mph in a straight line safe enough mate.

SteveOBHave · 23 Jan 2010 at 11:05

I would've thought the 300ZX would've been the better candidate but you have a very good point about the strength of the original engine parts. The Z engine parts gets unreliable once you get past 400BHP

Begbie · 23 Jan 2010 at 11:20

Wow, that could be very impressive.

Concrete · 23 Jan 2010 at 11:25

stulid said:
All serious rx7 have a V mounted cooling system surely?

This is what I was going to say, with a nice big vented bonnet/air dam to get the hot air out.

I hope you have budgetted for fitting a roll cage, and look forward to seeing your attempt!

stulid · 23 Jan 2010 at 11:32

Strange these videos aren't working.

Morba · 23 Jan 2010 at 11:34

technically you lost me before i started reading the first post, but my god, this looks like fun!

HUGE turbo!!!!

good luck fella. oh, the misses says you have too much money, but then she drives a 1.6 auto focus, so what does she know! lol