1.8 KR on ZX9R Bike carbs - How much power

lhasadreams said

On what factual basis can you claim that k-jet is garbage ?

Theres a reason Mechanical fueling has not been used in cars for years.  Carbs are still used today.  go figure

And they are ?
What cars leave the factory today with carbs ?
I would be surprised if you could find one that is not single or multipoint injection.
Still would like to see the power plots though !!

Lee_dub said

lhasadreams said

On what factual basis can you claim that k-jet is garbage ?

Theres a reason Mechanical fueling has not been used in cars for years.  Carbs are still used today.  go figure

Its not the full story, or a rational reason. Limiting it to cars, all cars these days use electronic FI for emissions reasons. In the same way EFI can meter fuel precisely enough to meet emissions requirements, it can be "chipped" or altered (indeed the manufacturer will do this at wide open throttle conditions, but not too much) to achieve best power or torque.

Mechanical FI, ie K-Jet as fitted to the Golf GTI, can't be tuned in quite the same way but it can be tuned, and achieve the optimal AFR for best power. In itself, it doesn't impose any particular restriction on the engine breathing either.

Carbs once properly set up, can also produce the ideal AFR for best power. However, since K-Jet can also be set up for best power, there is no gain to be made.

Once you start considering things like warming up, running on part throttle, etc then both carbs and K-Jet mechanical fuel injection are not as good as properly set up electronic fuel injection (especially if closed loop lambda feedback, which pretty much all are these days). However, K-Jet is better than a carb during warm up and part throttle. That's where carbs fall down, and why they were eventually replaced.

Well as per reading all the above, My statement about 90bhp and the scoobie were completley hypothetical I thought that was apparent, the idea was to scope some conversation which in a way it did, my main point was to extrapolate as to paul_c's comments "what is power", the truth of the matter is that my mk2 must have been pulling at least stock and with general rule of thumb and good tuning the carbs in the mk1 should make a difference, the figures on the graph show a similar result seemingly to paul_c with great result to 5.5k then an amout of leaning off that we couldnt resolve. however whilst driving it yesterday after the work was done the acceleration to 7.5k and climbing was phenominal. I do not however believe the result on the graph. to much power is going forward, as stated I have had to drive fast cars hard in the past for my job and have owned motorbikes that get to 60 in under 4 seconds. This car is more than the sum of its parts!!!!

lhasadreams said

And they are ?
What cars leave the factory today with carbs ?
I would be surprised if you could find one that is not single or multipoint injection.
Still would like to see the power plots though !!

didn't say cars specifically did I?

Lots of bikes still use carbs.  Anything mechanical cannot be as efficiant as EFI but k jet suffers badly with flatspots, no overrun cut off etc etc

Kjet = crap FACT!!

Oh by the way I should probibly add I run a 2.0 16v on kjet! How ironic!?

Brutal said

Well as per reading all the above, My statement about 90bhp and the scoobie were completley hypothetical I thought that was apparent, the idea was to scope some conversation which in a way it did, my main point was to extrapolate as to paul_c's comments "what is power", the truth of the matter is that my mk2 must have been pulling at least stock and with general rule of thumb and good tuning the carbs in the mk1 should make a difference, the figures on the graph show a similar result seemingly to paul_c with great result to 5.5k then an amout of leaning off that we couldnt resolve. however whilst driving it yesterday after the work was done the acceleration to 7.5k and climbing was phenominal. I do not however believe the result on the graph. to much power is going forward, as stated I have had to drive fast cars hard in the past for my job and have owned motorbikes that get to 60 in under 4 seconds. This car is more than the sum of its parts!!!!

Just post the results!!!!

Ok cant scan at the mo I will post it tomoz but it states 100.6bhp.

I dont think it is right.

There you go!!!

100bhp ?? thats 30 odd down on standard isn't it ??

is that at the flywheel or the wheels ??

geez if thats all you get mine will be out by saturday !!

Matt - Have you been reading this thread????

I bet you a tenner that if you take out the KR and put in a g60, we went toe to toe you would not get past me ….. my point being THE FIGURE ISN'T RIGHT!!!!!!

Hence the starting of this thread in the first place.

Are you going to believe the figure or the road!!!!

well figures usually lol

what did the guy at the rollers say to you ? his rollers can't be that far out surely ?

LOL 100bhp?

Thats at the wheels then for sure.

Built my old mans westfield lump which was a vauxhall 2.0xe lump, coscasthead, apr bolts etc, running jenvey throttle bodies and omex ecu.

RR @ 192 @8K at fly think the at wheels was below 140. which is still bonkers in a 600kg car lol

Now my mate has a dax with a 190 bhp bike lump running light weight chassis which is aroung 500kg and that thing is savage in comparison?

Thats it Matt exactly when we had finished the tune and I got my results I was bitterly disapointed, I have put a lot of time and effort in and was expecting a minimum 180bhp. The engine flew in the mk2 and  I used to beat mr2's and such all the time. When I drove it home what I got was not the expected 100bhp, I mean I have a honda with 130bhp, and This mk1 now flies. anyway I am going to try and sort a timed video out this weekend, thats all I can think of right now. But as I said you will not be disapointed (as long as you get it tuned).

to be honest bud i can't see how you was expecting 180 minimum for minimal work, flowed head and bike carbs can't add 50 bhp surely ? i'm gonna get my manifold built today and get these carbs on and book it in for a rejet / tune in all honesty i'll be happy at 150 and i ain't really expecting that

but fair play to ya mate if it is running 180

Matt

Is it "at the wheels" or flywheel bhp? It should say on the printout.

Power was at the wheels Paul.

Matt i did spend a lot of time researching this project before I took it on, and the amount of work wasn't minimal really. I just haven't got the cash at the mo for the exhaust and I dont see the point of bunging Schrick/kent cams in at the mo, I wanted to get the engine in and running right first before I went down that route., using the "if it aint broke dont fix it" train of thought, cams and exhaust are easy to do - they can wait…

IIRC a standard KR engine produces 139 bhp, so you were expecting a 30% increase in power from head work and bike carbs ?

I would love to see how the head was ported and polished because that is a serious gain in power from just head work.

Would expect to see a 14.5 sec quarter mile with 180bhp on tap - you going to run it on a timed strip ?

Have you got the power plots ? What sort of torque was it developing ?

This was my 8V G60 plot from 2007, it had a ported head, standard cam, supersprint downpipe and a 68mm pulley/chip - It was a 1H Rallye engine so 1763cc
A couple of chips were tried, used the Jabba one in the end…

Ill scan it in tonight and I am going to have a bit of fun with a drive, Hopefully a video too. Yes I will put it on a timed strip later in the year, The head has had a lot of work port polish and skimmed quite a bit, the carbs are expect to give a big bhp gain so no 180 isn't out of the question.
Again my real point is could the graph be wrong, I am certainly not trying to compete with anyone I wanted to see what results other were getting with the same setup before shouting my mouth of but nobody has yet given me that answer.

The carbs don't give any BHP gain, though.

I'd be more worried that the head work hasn't produced any sort of gain either. Who did the work, and what was done? Its something of a skilled art, its not just a case of removing lots of material, its the right amount, and where it comes off from.

Also normally on rolling roads they measure the inertia as the car freewheels through the transmission back to idling from full revs, take one from the other to get flywheel bhp - its worth doing this as the transmission losses do vary from one car to another, although you can normally assume a percentage etc.

The work was done for me by a very skilled engineering company up here, I seem to have perhaps opened a can of worms not really relating to my initial question.
I am not worried about what headwork has been done etc etc, I just wanted to know is it possible the rolling road figure could be wrong, I used to race minis as a kid I have built countless engines for personal use over the years from bikes to cars, I used to repair aircraft engines as a lad and served my apprenticeship doing so. I know carbs dont give any gains themself but they provide the vehicle with the means to do so.

My question….

Can these figures be wrong????

Looking forward to the answer