My 200mph budget build

[turbotoaster]

My 200mph budget build(now sponsored!!)

Im currently in the process of building a car that will do 200mph within the space of 1.7miles, with only a budget of £10,000

Just wondered if anyone would be interested in learning about it(got loads of pics etc)

 

[turbotoaster]

ok guys, didnt realise id get so many replies so quickly, ill start filling you in on the build below.

Been thinking about this for the last couple of months and ive decided to go for it!!

On another forum there was a debate about how much it would cost to do 200mph within 1.7miles(airfield)

The thread went a big barmy when everyone had all the little groups throwing there dummy out and a few extras pitching in for the fun, at the time i didnt really pay that much attention to it, just sort of skimmed to top of it.

Anyway while reading the one thing i picked up on was a magazine reporter from Redline, mr stav/steve. He claimed that you could go 200mph for £10k, of course everyone claimed that was rubbish but he stuck by his guns and made a few examples that made sense to me.

Yes you could build a multipurpose car that will happen to do 200mph with all the shiny alloy bits on and spend a fortune, but if you had one goal in mind and nothing else i believed it was possible.

Now i wont really turn this into a build thread as such as it will be probably be moved and id like to keep it here for everyone to see as i think this section brings in the most experience and knowledge

So a quick run down, the plan is to buy a car, tune it and make it run 200mph at brunters for £10k.

Already spent a long time chatting to guys who have done it before about this and hes give me lots of useful information and seems to back me up on this.

Spoke to Stav and hes gonna do a full magazine coverage and pay for the day etc so its a definite goer!

ill put my ideals below

 

[turbotoaster]

ok guys, the car im building is a mazda 1994 rx7

Ok to give you a run down on the situation.

I bought the car last april for £3000

The reason this car will work is that a lot of the things i require are already with the car.

It has a very low drag coefficient body 0.28 which means cutting through the air is easier, it has double wishbone suspension all around which adjustable camber from factory.

I have since fitted a set of tein coilovers with alloy top mounts, i got these from a friend who had only done 1000 dry miles on them for £300, this gives me the ability to make the car very low to help with aero, ie fast under, slow over creating downforce.

Now up until last year there has never been forged components for the rotary engine, its just something thats never been developed because of the complexity and the tooling cost.

This means that every power rotary engine has always used stock internals. Those 1300bhp rx7s you see at the drag strip are running the same bits that the guy up the street is running on his stock 250bhp rx7.

Now the benefit of this is the lack of parts that needs to be bought, when your going for big power on a piston engine most people 'forge' the bottom end by spending say £1k-£3k on rods, pistons and maybe a stroker crank.

Another benefit of this engine is the lack of cams, valves.

Now if you want more power from a piston engine you normally need more aggressive cams so you can get the air in and out a lot easier, which can cost a lot of money, some people pay up to £4k for a worked over head with lairy cams.

To do the same on a rotary all we need to do is port out the housings, now this costs anything from £200 put to £500 depending on where you go and what you have done.

For my engine, we have gone for a large port and also ported the inlet manifold, removed the extra throttle butterflies to help with flow.

This is the same as flowing the head and putting in more aggresive cams, gives the ability to make power higher in the rpms and also due to the extra flow of the port also means that the turbo will spool earlier.

Ill post this now and type the next bit up

 

[turbotoaster]

Errr, weight makes almost no difference at that speed!

weight can make it unstable, but within a limited distance the reduction of weight outweighs the negatives, if this was over say 3-4miles then yes i would agree keep the weight there, anyway next bit is written and will be below

 

[turbotoaster]

ok a few pics for you to see

the car when i bought it

tein coilovers added for height adjustability

bought the ride height down(this will be lower on the day, but need to drive the car to run the engine in)

 

[turbotoaster]

port timing...how high, low and wide you go affects timing, the bigger you go, the higher it will be making power.

On the issue of reliabilty, this is very much dependant on the tune of the ecu, unlike piston engines you do not go to knock then back off a couple of degrees, a piston engine will cope with a small amount of det before breaking, this is not true for a rotary, they cannot take any at all, the moment you get knock the 2mm metal seals that sit in the corners of the rotor break off and exit the engine.

So a 2mm bit of metal hold the explosion of a combustion chamber, its an awful lot to ask but thats what it was developed for and does very well.

Right so the engine was rebuilt with all new belts, bearings, seals all around the rotors and water seals all around the housings(kind of like a headgasket)

This came to a total of £3000, the reason for the large price is because I also had new housings put in, this was to make sure i had perfect compression to make the most power for the boost i was running, if not the bill would have been £700 less, £3000 i think is pretty good for an engine that can hold 700bhp, this includes a walk in/walk out service with a 12month warrantee.

ill add some pics of the rebuild so you can see whats going on inside it

ok engine build pictures
engine out and bay looking a bit dirty!!

removed secondary butterflies

inlet manifolds

throttlebody

engine plate porting

Housing ex porting

nice housing surface

 

[turbotoaster]

engine ready to build

Engine block built

bolt ons added for running engine in

to give you an idea of what stock ports are like and what my ports are like here is a pic

 

[turbotoaster]

Something similar was shown on Fifth Gear recently IIRC?

yes very similar only this time i thought about it more than listening to vicki butler hendeson giggling at me

I know a 630bhp VXR8 supercharged can reach 168 over a mile.

Wouldnt like to reckon it could reach the magic 200 in less than 0.7miles after that however. It gets exponentially harder as you get faster doesnt it ?

its all about drag to power, but weight comes into it as the faster you accelerate, the more distance you have for you 190-200mph push

Single turbo then?

yep, you shall it shortly

 

[turbotoaster]

From experience of many vmaxs, weight does not have an appreciable effect.

What power figure are you aiming for?

around 700bhp on race gas

 

[turbotoaster]

now when speaking to Rod(done 206mph) he mentioned to me that i would need roughly 630-650bhp to achieve 200mph, now thats in an ideal situation, ie im making that power at exactly 200mph, this brought me on to how much power do i actually need, the first thing to do is have a look around at a few compressor maps and also a few examples from the US/OZ

Now the problem with rotarys is they are very un-efficient with the airflow that they recieve, for every 10lb of air they receive they only make use of a max of 7.5lb of it.

So to make say 750bhp ill need a 1000bhp turbo if everyone follows me?

because of this un-efficent process the forces are not used fully for movement and are passed onto heat, hence why rotarys run so hot and also produce really high EGTs in turn because of the high EGTs the energy is passed out of the engine and into spooling a turbo, hence you can run a very large turbo for its engine capacity.

I did look at the garratt range of turbos but since this is very limited in budget i decided to discount them.

This left with me with a few other brands, mostly american diesel turbos. Now a company a few people may have heard off called Borg Warner are becoming increasingly popular in the performance market

Ill type up the next bit on my turbo choice in a second

 

[turbotoaster]

ok there are many different turbos from borg warner.

I have decided to go with a s475 which can flow 100lb/min with a 1.15 A/R rear end, i can go larger on the rear but decided this is a good compromise between spool and top end power.

I can give full specs of wheel sizes if anyone needs it

to give you an idea of size, here it is next to a coke can

It will normally outspool the equivalant GT4202 by 400rpm on a rotary and they ony cost £400-£600 from USA so a bit of a bargain!

Obviously you have this massive turbo, your gonna need to connect it to the engine, this is where a forum member on pf called rickylee comes into force.

Now after seeing his manifold he made on his turbo civic build thread, after seeing that i got in touch with him about making me a manifold, really nice chap and he will be building it, will also run a 5inch downpipe to help with spool and top end power which will exit behind the drivers side wheel.

Ill be using a 60mm wastegate and the manifold will be a t6 divided version to help out boost threshold

looks like this

Ill come onto cooling in the next post

 

[turbotoaster]

From experience of many vmaxs, weight does not have an appreciable effect.

What power figure are you aiming for?

I think you will probably need that and a bit more.

You can enter the first bend at brunters at 90mph or you can go from a standing start there, it will make very little difference.

What will you have in the way of brakes? You will need some very serious anchors to scrub off that kind of speed in the very limited amount of breaking space you have.

that power should be fine.

a 4 door corolla did 200mph there with 650bhp, with a larger front area and more transmission loses.

same for a escort cosworth with 700bhp

the car comes with very good brakes from factory, proper 4pots, there will be enough distance to stop dont worry

 

[turbotoaster]

now your throwing an awful lot of hot air around into an engine that is known to run hot anyway.

Without proper thinking its a recipy for disaster.

The standard radiator is around 30mm thick and does a decent job for a standard car but very quickly reaches its limit once your running a lot of power.

a lot of people choose to keep the stock one for a while when running single turbo, the reason for this is 2 fold.

1. because most single turbos are only oil cooled you have one less hot think to dump heat back into the water system.

2. because of the larger rear end of a single compared to the twins theres less restriction for the heat leaving the engine, this in turn helps get the heat out of the rotary engine faster, this was something i read and im sure theres a better way of typing it, but ill leave that for improvement.

Now im not just gonna run 400bhp on this engine, im looking nearly double that, so its silly to believe that the stock rad can cope.

Luckily the ebay rads you see for sale are only £120 and are proven to work on big power cars, they are 58mm thick which is a big improvement and are cheap as a bonus.
so got this one

The car runs 2 oil coolers as stock and they are pretty good at controlling oil temps even on heavily tuned rx7s.

The next thing to come up is air temps, running 30psi+ on a massive turbo will cause high temps.

To get over this i decided to use the cossie way of dealing with them and get a rs500 intercooler, now normally they are 50mm in depth, this is fine im sure for 500bhp(i know rod used one at 600bhp) but im going for more than that and want to make life easier for myself so im going for a 70mm core version which should give me the cooling that i require. This i havent ordered yet as need to save a couple more months for

here below is a picture of the setup...only in paint but gives you an idea

now blue is intercooler, red is radiator and green is fans, the grey is the aluminum ducting which ill go all around the cooler so that no air is wasted and will then be forced through the rad aswell

also it will be keeping a stock front end, the front opening will give enough air to the cooler as the ducting will make a funnel shape to the cooler, if air looses a few mph before it gets to the cooler it wont matter at 150mph+

ok fueling next

 

[turbotoaster]

well ill be going with a power fc, its easy to tune and pretty versatile
It arrived in the post today actually from japan.

yes something like a autronic/motec would be better but theres some big numbers being done over in the states on this ecu and money is an issue.

The good thing about it is the commander which can monitor everything the ecu sees, saves me buying a few gauges, for example at can see all the below in real time

Engine RPM
Ignition Timing
Vehicle Speed
Air Flow Voltage (Pressure Sensor Voltage)
Injector Duty Cycle
Boost
Knocking Level
Battery Voltage
Intake Air Temp
Water Temp

Thinking about injectors i did some calculations and for 700bhp a rotary needs 5500cc/min of fuel(not 100% duty, about 85%)

now ross at dragon performace and the guys at reworx both suggested i go with 6 injectors instead of trying to fit massive injectors into the primarys and secondarys as its a lot harder to map.

so we talked about maybe 6 x1000cc injectors, but then that comes down to budget again.

I was watching a guy in america running 9s quarters running a stock ecu with a peter farell piggy back ecu controlling extra injectors, he was pushing 600whp+ which is the numbers im after.

i sat and thought about it a couple a nights ago and thought how can i do it.

it then came to me, i already have 2800cc of the injectors in the car at the moment, i only need another 2700cc and im sorted, both tuners recommended 6 injectors, so why dont i put 2 x 1600cc injectors in, that 3200cc worth of fuel, more than enough, watched a few videos of some monster rx3 and he was running extra injectors in his Upper Inlet Manifold and ive decided thats where they are gonna go, on the secondary port sides(outer edges) this means i keep my stock primarys for driving around like miss daisy, also keeps my afr while idling as normal and normal driving ill be ok

Fuel pumps will be 2x 305ltr pumps running in tank which will give me more than enough fueling

 

[turbotoaster]

I would have thought something along the lines of an MR2/RX7 would be good for this.

I know the RX7 can take massive boost on stock rotors. Always see them with T88's etc running over 400bhp. I'm not clued up much on 13B tuning but know they can take a lot of boost due to being rotary.

There is a chap in the US who has a 185 celica running a 800hp 3S-GTE who did 200mph

well yes rotarys can take a lot of boost but only on race gas or with something to slow the burn rate down to stop det...ie water injection or E85 fuel.

on normal pump fuel they cant at all, normally 1bar of boost is the limit no matter what turbo as above that your playing with fire.

a t88 on pump fuel is about 530bhp@1bar or [email protected] on race fuel

i couldnt do 200mph in one mile, wouldnt be able to hook up till 4th gear lol

 

[turbotoaster]

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]

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]

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

 

[turbotoaster]

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

 

[turbotoaster]

All serious rx7 have a V mounted cooling system surely?

track cars yes, the reason for that is to split the air between both the rad and the intercooler, the reason being if your thrashing it for 20mins on track water temps start to rise due to not enough air getting to the rad.

Since my setup forces all air to go through the intercooler and rad this wont be an issue.

the problem you have with v mounts is you need a vented bonnet to make them effective, all well and good but then you are compromising your aero package by creating drag, fine for tracks when you dont go that fast, but not for top speed

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.

the car does 158mph from factory, one of its strengths is its high speed stability over other cars, diffusers and canards help you when your cornering and you need the downforce, in a straight line this is not required unless without enough downforce you break traction, this will not be an issue from 4th gear upwards

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

I earn a lot less money than you think, infact less than 90% of the people on here, i work part time in a call centre while im trying to get into the raf.