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honda cbr1000 x2 sports racer
ANDYSHORT - 8/1/08 at 11:51 PM

hi everybody what a fantastic forum you have just found it last nite wow! i hope you can answer some quetions i have about the cbr1000f engines i have in the car ive been building i have a few but i will start with a couple - has anyone had trouble with oil surge ie do they have to be dry sumped ? can i dismiss the oil cooler and join the pipes with a piece of hose (bearing in mind that its only used in short bursts ) also what do others do for air filters i have removed the intake trumpets from the airbox so i have rubber trumpets on the carbs what does everybodyelse do?im sure i have other questions i will leave that for a nother time!by the way the car will be used for sprinting i have done a lot in saloons and won my class in the british championship so the next step was something faster so i decided to build some thing from scratch everything you see i have made apart from the body which i bought and then modified i will try to post a couple of pictures . ANY COMMENTS WELCOME

[Edited on 11/1/08 by ANDYSHORT]

matt.c - 8/1/08 at 11:56 PM

Have a word with ANDY at AB performance. He loves HONDA's

AB PERFORMANCE WEBSITE

Oh yeh WELCOME to the madhouse.

[Edited on 8/1/08 by matt.c]

russbost - 9/1/08 at 07:37 AM

Hi & welcome, watch out for anyone wearing a white coat
Sounds an interesting project, haven't heard of surge probs with the cbr, but I'm a Kawasaki man, I know they don't behave well without some sort of airbox or dejetting & trumpets but can't answer for the Honda. Can't see any reason why the oil coolers can't be removed if only used for sprinting, the oil won't have time to get up to temperature.

ChrisGamlin - 9/1/08 at 08:56 PM

Hi Andy, welcome to the forum

The CBR1000F engines have proven to be pretty bulletproof and don't seem to suffer from oil surge in kits, but if you're planning on running wide sticky slicks for sprinting, the same may not apply so yo'd need to keep an eye on it.

However, can I ask the reason you're fitting two? Assuming its for more performance, its worth bearing in mind that each engine weighs about 85-90kgs and will give you about 125bhp, so you'd almost certainly get very similar performance out of a more powerful single bike engine that will mean a lighter car, something like a ZX12 or even one of the latest banshee 1000cc engines (ZX10RR etc) that only weigh around 60kgs yet kick out over 180bhp! I know the engine costs are higher, but overall a twin won't be cheaper, and a single engine will be far less complicated so more reliable.

cheers
Chris

NS Dev - 10/1/08 at 11:17 AM

Not that simple Chris.

They might make 125hp but at what, 9000 revs, 10,000 revs??

You have to pull though to those revs and off the start of a sprint with sticky slicks you need a lot of torque.

The twin engines won't help that much in terms of absolute power to weight compared to a tuned biek engine, but they give you double the torque at the wheels (ish) for your extra 85kg, which make a big difference at the start and out of the slower corners.

All very well having a single tuned engine but improving cylinder filling at low revs on most bike engines is not easy, with most its pretty much more revs = more power.

Its not all top end power, in just the same way as its not all bottom end torque either!

ChrisGamlin - 10/1/08 at 08:48 PM

Not that simple either though

Engine torque will be higher and wheel torque (which what matters, as you know) may still be higher too, but nowhere near double.

For starters there's going to be a significant additional transmission loss involved in getting power through two gearboxes and a transfer box, so although you start off with around 250bhp and 140lbft at the cranks, you might only see 200bhp at the wheels and a similar percentage loss in useable torque down to about 110lbft. Compare that to around 160bhp and 85lbft at the wheels for a ZX12 then even assuming the same gearing, its only about 25-30% more power / torque at the wheels.

The ZX12 revs to about 12k though rather than 10k, so it can be geared around 20% lower whilst retaining the same top speed, which means another ~20% gain in wheel torque, so you're almost getting into single figure advantages now even without the additional weight to consider. If the weight is even 10% less with the single, you've all but cancelled out the advantage of the twin in all respects.

I can see where you're coming from and the above figures are only an example and may not be hugely accurate, but they're not far out so I'd wager a fiver that it wouldnt be much quicker or any cheaper to build, and Id wager my house that it wouldn't be as reliable!

cheers
Chris

[Edited on 10/1/08 by ChrisGamlin]

NS Dev - 10/1/08 at 09:43 PM

Agree totally on reliability and build cost, former will be poorer and cost will be as much as tuning the single engine.

Torque at the the wheels will be very close on double though as the single engine would have hypothetically as you know! ) the same gearbox as the twin engines would.

On my grasser its just a case of two chains instead of one, so still one per engine (so still double the torque)

I know where you are coming from, and to be honest if I were building a tarmac car I don't think I would use twin engines, but then I have seen a fiercely quick OMS twin bike engine sportscar demolish the opposition at some sprint meetings!

NS Dev - 10/1/08 at 09:46 PM

here's the one:








ANDYSHORT - 10/1/08 at 10:28 PM

hi guys thanks for the reply,s, to answer a few questions the reson i went for the twin engine route was just to be different! . since starting the project a nother twin has appeared at gurston down hillclimb ,a twin hyabussa built by force racing cars although this was a money no obgect car and is very quick obviosly my effort is on a very limited budget!! im sure i will have lots of teething trobles but surely thats all part of development? im pretty sure i can eventually make it work, but how succesfull we will see! i have done a lot of hillclimbing and sprinting (winning my class in the british sprint championship in 2002 ) when i last competed ,and i still go and spectate when i can .

ChrisGamlin - 10/1/08 at 11:06 PM

quote:
Originally posted by NS Dev
Torque at the the wheels will be very close on double though as the single engine would have hypothetically as you know! ) the same gearbox as the twin engines would.


If we were comparing 2 CBRs against 1 CBR with no transfer box, I'd agree that it would be near double, but a ZX12 is nearly 50% more powerful, 30% more torquey and revs higher so can be geared lower, and Im not sure you could get away without a transfer box on a circuit car so I'll still maintain that its nowhere near double

Dont forget that torque at the wheels isnt a direct indicator of torque at the crank, because the available torque at the crank gets multiplied by the gearing to give a figure at the wheels, so although the ZX12 may start off with a ~70lbft disadvantage at the crank compared to two CBR1000s, the gearing (and transmission loss) differences will reduce that further as I mentioned in more detail above.

quote:

On my grasser its just a case of two chains instead of one, so still one per engine (so still double the torque)


Yep that will certainly negate the additional transmission loss of a transfer box, but is that layout feasible in a circuit car as Im assuming you don't have a diff in the Grasser and just drive the rear axle directly? If you need a diff then you need to get the two engine outputs into one before feeding that to the diff, which means some kind of transfer box Id think?

cheers
Chris

[Edited on 10/1/08 by ChrisGamlin]

thomas4age - 11/1/08 at 07:38 AM

Wow, now that's a nice bit of kit right there.

is that a Norma?

and how was the drive train configured, It looks like a normal diff in the rear of that twin engined beasty.

this discussion has been comming and going for a couple of years now, but keeps intriguing me.
imagine getting into you car at the cafe on the roundabout of Arnage and firing up 1 engine, and then when the whole beer gulping crowd has got up to see what's cooking, you fire another one.....

grtz Thomas

[Edited on 11/1/08 by thomas4age]