nigelb6969
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| posted on 4/10/17 at 03:24 PM |
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Throttle Bodies
Hi, looking for some advice. I have a Zetec silvertop which has been built to a very high standard currently running 4 Yamaha R1 bike carbs and a
Camens ECU. It's on full race cams. It revs to 8000. I only get a powerband from 4000rpm which makes it a pig to drive on the public roads.
It's been on a Dyno and is showing 194BHP at 6000rpm. I've been told a throttle body kit will sort out the engine and make it more
tractable without it losing too much power. What could you all advise me please?
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SPYDER
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| posted on 4/10/17 at 04:00 PM |
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Hi there. What happens to the power after 6000rpm? It would still be increasing on standard cams, never mind race ones. If you fit the correct size
throttle bodies you shouldn't be losing power at all. You should be gaining some.
A properly set up set of throttle bodies will make your engine as tractable as it can be, given the limitations of your "full race" cams.
Maybe not pulling cleanly from low revs but as near to that as possible.
I have re-spaced 42mm GSXR750 bodies on my 3SGE Toyota engined car. It, coincidentally, is producing 194 hp but on standard cams. It is well mapped,
by myself, subsequently checked on a RR. It pulls from nothing. Standard cams though.
I would recommend GSXR 750 or 1000 bodies, preferably earlier ones that can be spaced correctly. Should be good for 200hp, maybe more. Hayabusa ones
are a little bigger. 45mm I think and will be better if you are targetting 220+.
If you have deep pockets there are plenty of kits from Jenvey et al that may even give more power than similar sized bike bodies. I'm not
getting into that argument.
Inlet tract length is a factor too. And butterfly and injector position. Get googling. Tons of info re. Zetec ITB conversions.
What is the spec of your cams? What max power should you be expecting?
[Edited on 4/10/17 by SPYDER]
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Nickp
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| posted on 4/10/17 at 05:09 PM |
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As above, doesn't make sense if your peak power is at 6krpm yet it revs to 8krpm. Have you got a dyno graph? What size are the carbs?
I built a Fiat / Lancia twin cam, that coincidentally made 194bhp on race cams, carbs and Canems ign ECU. It peaked around 7krpm and would pull
cleanly from around 3krpm even on carbs.
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nigelb6969
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| posted on 4/10/17 at 07:19 PM |
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It revs to 8000 but the guy on the dyno backed off at 6000 as the engine isn't ran in yet. Not sure on the carb sizes just that they are R1
Yamaha. I'm starting to learn a bit more about the engine as time goes on. Dyno guy says at 8000 it should be showing around 225BHP. I just want
tractability and if necessary at the expense of a little BHP. Cams are Stage 4 Pipers and have Vernier wheels. I don't want to get ripped off
and end up buying stuff I don't need but would like the car to be driveable. Thanks for your advive so far, much appreciated.
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SPYDER
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| posted on 4/10/17 at 08:05 PM |
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Hi again. If you are aiming at 225hp then I suggest Hayabusa throttle bodies or similar. I would normally say that if you don't mind losing a
few but gaining on driveability and road manners then go with GSXR1000 size. The injectors might be close to their limit though.
However, you might never have much in the way of driveability on full race cams, they just aren't designed for that.
Whatever you do, get your car run in on your present set up first.
I would also consider fitting a larger cable quadrant in place of the tiny one usually found on bikes. It will give a longer and more controllable
action.
Does the CANEMS ecu allow for any self tuning like my Megasquirt does, or is it all done on RR?
And "get googling!"
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SJ
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| posted on 4/10/17 at 08:33 PM |
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First question would be what has been done to the R1 carbs to set them up for the Engine?
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Nickp
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| posted on 4/10/17 at 09:09 PM |
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If you get it properly set up on the correct ITBs and you're still not happy with its tractability you could always look at the cam timing.
The cams in my twin cam were supposed to be set at 100deg according to the spec sheet. I backed them both off to 108deg in the end. It was much more
tractable yet still revved really well 
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snapper
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| posted on 5/10/17 at 06:26 AM |
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I think this a typically over cammed engine.
There is a lot more to power than just going for full race cams, head work and compression ratio so important.
On the road if your not producing any usable power until 4K it just won't be usable, you'll either be screaming in all gears or in the
wrong gear
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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Nickp
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| posted on 5/10/17 at 07:07 AM |
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quote:
Originally posted by snapper
I think this a typically over cammed engine.
There is a lot more to power than just going for full race cams, head work and compression ratio so important.
On the road if your not producing any usable power until 4K it just won't be usable, you'll either be screaming in all gears or in the
wrong gear
You may be right but he does start by saying it's built to a high standard. To me this means it'll have headwork and increased CR to match
the cam specs, if not then it just isn't. I'll be surprised if big improvements can't be made by fitting FI (with correct mapping)
and cam timing 'tweaks'.
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peter030371
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| posted on 5/10/17 at 08:38 AM |
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Lots of questions spring to mind from reading all the posts here.
1) Are you on carbs as you say in your first post or fuel injection?
2) If carbs what has been done to the jets (and by who)?
3) What rolling road did you take it too?
4) By 'stage 4' cams I assume you mean full race cams? If so they are specified to give power only above 3500rpm which is what you are
seeing. They are also specified to give peak power (depending on the rest of the engine spec) around 8500rpm which is above your limit.
5) Why have you gone for race cams on a road car?
6) Proper throttle bodies (Omex etc) would be the best way to go. Bike bodies can be made to work but part throttle response and driveablity are more
difficult to get right and if you already have problems with low end why risk it (again)?
I remember a quote on another forum that said 'what do i need to get 220+bhp from a Zetec' and the best answer was '...very deep
pockets, or a Turbo (and very deep pockets)'. Hence I started out with a Duratec 
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nigelb6969
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| posted on 5/10/17 at 01:01 PM |
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Hi guys. I inherited the car from my uncle who passed away. The engine spec is as follows: Ross forged pistons, steel crank and conrods with Arp
bolts.
Fully gas-flowed cylinder head with solid lifters and big valves. Lotus profile race cams.
Yamaha R1 bike carbs set up by Bogg Brothers, Custom built 4-2-1 stainless manifold and system. Aluminium lightened flywheel and EBC heavy duty
clutch. Type 9 5 speed box. The Canems ECU is only mappable by them on the rolling road where it was measured. For simplicity I'm going with the
Jenvey or Omex throttle bodies with either the Emerald or Omex ECU.I am taking it to one of the best tuners in the country for rectification.
I think my uncle was given the wrong info so my aim as a tribute to him is to get the car right. You've all been a great help and I thank you
all. Nigel.
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nigelb6969
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| posted on 5/10/17 at 01:06 PM |
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Sorry, missed the cams, they are custom Pipers with Vernier wheels. I'll let you know how we get on with the development, Nigel.
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mcerd1
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| posted on 5/10/17 at 01:54 PM |
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quote:
Originally posted by nigelb6969
....Not sure on the carb sizes just that they are R1 Yamaha....
They are around a 40mm choke - very roughly speaking you could compare them to twin 45's
which would probably be a bit on the small side for a 2.0 engine at 8000 rpm
looking at it another way your trying to get 225 bhp out of carbs from highly tuned bike that only made ~140 / 160 (they can make more power, but
they will start to struggle eventually )
you can get bigger bike carb's (blackbird ones are ~42mm which are closer to twin 48's) but the more you tune for top end power the more
you'll loose in drivabilty on the street 
going to EFI could help manage the compromises between a street vs race engine - but its not exactly the cheap option...
(using Megasquirt and bike TB's can keep the costs down a bit - Jenvey's and a big name ECU may well be easier, but you pay a fair bit
more for that convenience)
and even the best EFI system can't guarantee that you'll not still want to change the cam's later - but thats a question of your
preference / what you'll put up with on the road (and also as mentioned above - what effective gearing you have....)
-
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nigelb6969
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| posted on 5/10/17 at 02:29 PM |
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Thanks, for all your advice, I'll keep you posted on developments. Nigel.
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rusty nuts
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| posted on 5/10/17 at 04:27 PM |
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Can't help thinking a decent pair of road cams would make things easier?
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SPYDER
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| posted on 5/10/17 at 07:37 PM |
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^^^^^^^^^^ Go for GSXR tb's and Megasquirt and the money saved will buy the cams. Aim for a solid 200hp at 7000rpm and you can have all the
driveability you could wish for! The engine will be under-stressed too.
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