ImaRacing 700

So what is the best option?I want 600plus BHP...is it better to run a GT40 or 42 at a lower boost pressure than run a GT35 at over 30psi???Not too worried about lag as i am gonna be running a drivable comp ratio...PLUS on dyno for a laugh i could probably wind a GT42 to show an impressive 700plus bhp but incar let it be run around 600bhp

cossiemanden

That depends on what you are going to use the car for, but the bigger the better they say...
The bigger turbo, the more rpm before boost come on, but the harder it comes
If you are going for 1/4 mile racing then go for the GT40 or GT42

ImaRacing 700

Nope just 1 top speed run to try and pass 190mph DIY stylee

Dont care about lag....but my rev limit will be 8000rpm no more..so dont really want a turbo that spools up at 7000rpm

Rick

Go for the 40 imo

PhilM

Work out the airflow your engine will require for the power output (torque/revs) desired. And then consult the compressor maps to find a suitable turbo to do the job.

Stavros

what sort of compression you talking about when you say sensible? you going to use pump or race fuel?

ImaRacing 700

Pump fuel for dyno as i want a real figure ...Comp ratio is secret at the mo so infact is the whole spec full stop TBH bar the fact its on 8 greys and S8 management ...for the top speed run race fuel will be used and i dont consider it cheating as its for safety as it wont be mapped for it!

PhilM

You make it sound soooo easy!!! I just wish everything could be that easy, im having a nightmare fixing the leak on my washing machine!

If the whole engine spec is a secret, how can people help suggest the correct turbo for your engine.

Ryan

only a 8k limiter

Why so low?

Escpecially when using such a large turbo.

ImaRacing 700

PhilM this is monte spec by ME It may only produce 400bhp but then again it may go 700plus who knows...but 2005 will see

Ryan...going above 8k is not sensible full stop...anybody that says it is obviously has no experience and hoping for the best ....Peek power from a gt42 is around 7500rpm anyway so thats enuff to get a big figure...top speed at 8k using correct gearing would be over 200mph and i bet a 42 could rev to that all it has to do is not let go on its one run...once top speed recorded it can blow up if it wishes...the hardest is getting it to stay together if this is gonna work its gotta be a nice drive off boost as lets be honest on a public highway i wont be able to put my foot down and reach positive boost for fear of soiling

Stavros

700+ on pump fuel i can understand, its just you say a "driveable" compression ratio, and to me when people say that, they mean quite high, which dont work IMO unless you got some very special anti-det pistons n combustion chambers, which you wont have.

remember comp ratio has little to do with when the boost threshold starts, thats more to do with head n cam spec.

are you mapping it?

PhilM

Phil, only joking mate, wish you the best of luck with it Youve proved a few poeple wrong already I think

ImaRacing 700

I will be with it on Dyno so i will learn and input but probably be told to shut up..ROFL.....only one person will know of dyno day as this could be the most embarrasing day of my life when it lets go on dyno cause i forgot to torque the big end bolts

Stu @ M Developments

iTrader: (12)

Good Luck Phil.... its gonne be good

Ryan

Isnt that completely dependant on headwork and cam's????

Just out of curriousity are you using standard rods? or H section ones?

Good luck what ever choice of Turbo you make! I've already made my choice and it aint a GT.

I would be over the moon if my engine got anywhere near 600

ImaRacing 700

Ryan its good head and appropiate cams IMO

Rods IS a good question...not 100% deceided maybe Arrows or maybe 4x4 rods with the H on them resized/balanced and shot peened...TBH i cant get much advice on it as everyone who does this kinda engine goes mad on new internals so the limit of std parts hasnt really been tested YET imo ...although i know of a 750bhp plus on std bottom end in rally cross and seems to be holding out....Alot to think about and cost has to be considered as if a choose something wrong its gonna blow along with expensive parts...rest assured if i am happy then it *should* hold together....

Ryan

I'm using standard rods which have been shot peened and micro polished.

Stavros

I think IMAs right about std rods (when shot peened etc), as with the crank, i dont think a 100% limit has been found (in a PROPERLY working engine) has it?

Ive asked before, but has anyone broke a cossie crank or rod that wasnt due to det or oil issues?

If hes doing a budget job, id stick with em n see what happens, esp as it dont look like your revving it mega high

cossiemanden

Go for the gt-40 or 42 depending on trim on them...

The turboes are good enough for street also, BUT cams and head are tha main factor here:=)

Rene

is it going with a BANG?!


soz phil it was screaming for that quote!

good luck!

Benn 304R

HOPE ALL GOES WELL FOR YA M8

dannyblackpool

Gaaables

best of luck mate, will be good to hear your results

Mike Rainbird

iTrader: (3)

Phil,
You're STILL not going to find the limit of the crank and rods then are you?

To find the limit, you have to keep increasing boost / revs etc until you EXCEED the limit (and then BOOM) Obviously the point before the BOOM is the limit .

If all you want is 600bhp, then the GT35 is the turbo for you , going for bigger will make it too laggy and mean that it is an all or nothing car - which is very hard to drive or put the power down. With the correct head, cams, inlet manifold and exhaust manifold it will make this power at around 2 bar .

Anonymous

Sounds to me like you need to make your mind up a bit more certainly exactly what you want to be achieving with the engine first, then match the spec to that.

If its out and out horsepower then i think you are silly not to use a set of arrow rods or similar so they can actually handle some det, with the best will in the world when you are mapping it if you are looking for the absolute limit of power from the spec you have then there are bound to be times when it ends up the wrong side of safe briefly on the dyno, at those points in time i would want arrow rods personally.

As far as finding a limit of the standard rods go, like any production rod they are going to vary anyway, and there is far more to it than just they can take "X" bhp, so many different factors in there which determine the stresses the rods are going to experience, including things like how straight the bores are relative to the bearing tunnel and stuff like that, who is preperaring the block for you becuase getting the basics like that right is going to be totally crucial on an engine of that spec.

CossieRich

iTrader: (1)

so whats happenin to the engine you have just built phil?

ADUSR33

phil ur hunk of junk will never see 600hp proven nevermind 700hp ..

And u call steve for dreaming

ImaRacing 700

ADUS....how much you willing to bet?

Rich....i dont know yet...i may use part from it not sure.

The biggest dilema is stick to 600bhp on gt35...or go gt42 and say fuck it...on the right fuel the car will make over 700bhp but will a std crank (a brand new one) hold together?...I think after having words the rods are the weak link so its gonna have to be arrows IF i go GT42 or i may use them anyway.

Mike...the car will have everything below turbo have no fear BUT on boost it would be mental at say 2bar 200mph a deffo if it will last a couple of runs at the pressure...then simply turn it down to say 1 bar and have maybe a nice 450bhp..although fooking laggy but that aint an issue.

I dont want to get 600bhp then say i wish i'd gone 700bhp but then again is it worth the extra risk as this is a budget engine DIY style ...but what if it holds togther?......

Do you feel lucky,Punk?....

Anonymous

Have you got any idea at all what you are doing?

I dont mean to be rude, but it really doesnt sound like it!

ImaRacing 700

Chip i know nothing thats why it will shock the world!

Ryan

nail

&

coffin

Anonymous

LOL, well i'll look forward to be shocked along with everyone else i guess.

Good luck with it anyway.

ImaRacing 700

Please keep doubting ....its gonna give me much more satisfaction *if* i acheive it....

You can read all the books in the world and think you know shit...but unless you DO it you are a noboby

RANJ

spot on

Stuart.W

Did you mention where you wanted to do 200mph?
If Bruntingthorpe then it'll make it 10 times more difficult even with a GT42.
You might find it easier and cheaper to do 215mph on an open road than 195mph at brunters.

I'd only use a GT35 on a well spec'd engine, it would certainly be cheaper to use a GT40 or 42 on a less well spec'd engine to give you what you want.

Hope you get there (wherever it is you're going)

Anonymous

Stuart, very good point, its a whole different ball game in a confined space.

Azrael

I watched "High Octane" today and they showed there Scoobie pushing 700bhp on wheels!! from GT-35. Wonder if that was different bhp or what ...

Cam

Its a 2.5 conversion running 2+ bar boost so 700hp seems about right.

Martin-Hadland

iTrader: (2)

its gona have to be one special gt35 to produce 700hp at the wheels!

Azrael

That's what I thought when I hearb about it.

Well I checked the video once more. Maybe it's 700bhp at crank. Still I saw here on forums that some people put even bigger turbos on their Cpssies and non make 700bhp. Why bigger turbo when this still has potential? YB won't manage that kind of boost?