Daft Question re Throttle Bodies

[Buda]

Sorry (in advance), this is probably a daft question to some but for the benefit of people like me can someone, in simple terms, explain what changing/adding? throttle bodies to a rover 1.6K engine does, by the way could some one also tell me what they are etc. At present all I know is that they are expensive, make you go faster and that I really want some, (thats advertising for you, I'm just a mug, must go the bettaware person just popped a new catalogue through the door, mmmmmmmmmmm small bag closing thingies)

[oilyhands]

In laymans terms adding a set of TBs should make the engine a lot more responsive through the rev range, peak power should go up a little too.

 

TBs are the injection equivalent of adding a pair of webers to your engine and give one barrel per inlet port. Most injected engines come with a single throttle body and a convoluted plenum as original equipment, this is the injection equivalent of a single downdraught carburettor.

 

For more detailed info try here.

 

(URL now corrected , thanks to the great Fjord designer)

 

Oily

 

Edited by - oilyhands on 10 Jan 2002 11:29:08

[Alex Wong1697456877]

TB's really do come into their own when you start using peakier cams. The ability to control the timing and fuel delivery with throttle position and revs is much greater with throttle bodies rather than carbs. Oily's pages explain everything you need to know.

[Red SLR]

I fitted a set to my K about 8 months ago, the engine was a lot sharper as a result and I got about 10bhp for my troubles! The only thing I would suggest is to stick with well known ECUs such as Emerald and follow the advice of people who know what they are talking about such as Oily, at the time I did not fit a water return pipe as the TB supplier told me it was not needed, a lot of people on this forum told me to fit it, but I didnt. As a result I got loads of air locks and hours of trouble fixing it, I am now getting this fitted.

 

The other thing is once you start upgrading you will never stop! I am upgrading my head now and looking for more power, and I am already thinking about pistons for next winter... teeth.gif

 

X777CAT

[Slarty Blat Fast]

Sorry, oily. I think yuo got a slash where yuo wanted a dot.

 

Try here

 

Slarty Blat Fasttongue.gif

[yankeedoodoo]

Can you post the actual web address for that site. Thank you!!

 

 

[Blatman]

If you hover your pointer over the link, the url should be displayed on the bottom left of the screen, just above the start button. Or you can right click the link, select "Open link in new window", and voila, a new window with the url in the address bar..........thumbsup.gif

I'm assuming Windows useage here, before all you mac users pipe uptongue.gif

[yankeedoodoo]

Blatman, Thanks! Got it. My computer illiteracy shines through again. Just another ignorant colonial lad. Humbly, yankeedoodoo

 

 

[Taran Las]

Or, Right click the link - Select properties and the URL will be given in full.

 

Phil Owen.

[Bob Corb]

The reason that port throttle bodies respond better is

 

1) The lack of volume in the plenum

2) The set up of the engine management can be a bit fruity (i.e. lots of fuel enrichment during transients).Which Rover couldn't do in the base vehicle due to constraints on vehicle emmisions which are significantly harder to pass than the MOT that we have to get through

 

Benefits could be made in area 2) with an aftermarket ECU while sticking to the normal plenum based inlet system. This will allow a broader spread of torque due to the tuning effect of the plenum volume but will be a little more restrictive to airflow which will hamper max power. Power isn't everything. Throttle bodies will knock low end torque down below 3000rpm and idle quality will probably suffer.

 

Buy them anyway, they look nice.

 

BC

[Tony Martyr]

All these replies should lead one to ask the question 'If TBs are mechanically simple and give better control - why aren't they the default design?'

Complex shaped plenums (plenii?) are not developed for fun but to give good throttle response over the normal driving range. The price is that they, to a degree restrict beathing.

But there is a downside which is dealt with via driving techneque and mapping. Because there is a very low volume of air between the cylinder and butterfly there can be a hesitation in the engine responding to the throttle from idle. With a plenum design there is sufficient air stored for the system to respond. Normal town drivers would find this stutter from idle unacceptable we just deal with it like we deal with low inertia flywheels and not stalling at traffic lights

[oilyhands]

Tony,

 

While agree with your comments about the plenums buffering of air which helps transients, a bigger problem must surely be the response of the ECU/injectors, in that during a transient the calculated modulation of fuel, is that for the previous engine cycle..

 

When using bigger cams, the plenums volume works against you, especially at idle where the reversion pulses disturb the plenum and the other cylinders resulting in a very bad idle/transient indeed. The lower volume of air with a TB setup and the fact that the butterfly sides are not connected as in a plenum makes the TBs far more suitable in these instances.

 

Oily

[Peter Carmichael]

I cannot agree that a plenum improves transients. IME the plenum is responsible for the revs hanging when the throttle is closed, causing significant issues that you have to learn to drive around to make smooth progress. Gear changes take a long time also while you wait around for the revs to drop.

 

Plenums are mostly about cost engineering and simplicity. There may be some advantage when driving between idle and 1500rpm, but it is one hell of a compromise to make. 99% of modern cars have worse throttle response than a single carbed mini.

 

I have just about got my throttle response how I want it now with throttle bodies and very low inertia. All the modifications have just gone to make the car easier and easier to drive, with the notable exception of pulling away from a standstill.

[Buda]

Thanks very much all, just finished reading oilies link page (v helpful). So now I know what they do/are here's the crux, I've got a standard 1.6K engine and limited funds but obviusly want to increase the performance over time without buying bits that I'll end up replacing in couple of years, in my mind this means buy the best now with the end result in mind. So am I right in sorting one bit out i.e. breathing, then exhaust, then cams etc or should I just buy Supersport coversion off Caterham and use this as a base (bearing in mind that my overall aim is not to stay at 138bhp but eventually exceed it.(will I want to replace the supersport bits eventually?)

 

I did however read in another thread that one could buy a short VVC engine relativley cheap, would it be a better proposition to attempt to build up a larger capacity engine myself (sounds like fun - and a hell of a learning curve from technical lego engines!) and reap the benifits all at once if I ever manage to complete it?

 

 

 

 

[robmar]

Buda - the supersport kit, although a good piece of kit is a dead end if you want more power later on

 

IMO - you could look at upgrade in the following path

 

Prog ECU

TB's

Exhaust

cams

head porting

steel bits

 

rob

 

[Peter Carmichael]

Whatever happens, we have to get you away from the standard 1.6 ASAP. The difference between peak power at 5500 and peak Supersport power at 7000 is a big difference.

 

If you want a Supersport kit, don't pay top price for a new one when others who have upgraded will have them kicking around. I am sure you should be able to find one for a lot less.

 

The standard exhaust with the 4-1 inside the engine bay holds back all the engines, so the sooner you can go to a competition style 4-1 the better. Supersport on a competition exhaust is a nice combination.

 

Rob is suggesting a route that takes in some enabling technologies - throttle bodies and programmable ECU. The problem is that if you spend a grand on these you won't get much of a result because you still have asthmatic standard cams, standard valves and standard porting. It will be 1500 quid by the time you have the exhaust on as well and you will still have standard cams. Dave Andrews gives good advice when he recommends that you need to match tuning effort across the board, but from your starting point it will be 2500 quid before you reach the Nirvana of a ported, throttle-bodied 180bhp.

 

Everybody who has gone down a tuning path will tell you that it takes a lot longer than you ever expect. If it is your only engine that means time with the car unusable in the garage.

[Peter Carmichael]

Oh I should have said...

 

Doing a DIY Supersport kit could be an option, with suitable hydraulic cams from Piper, a programmable ECU. Save the throttle bodies for later and get a competition exhaust first.

 

The only throwaway element would be the cams if you didn't go far enough in the first step, so I would be tempted to get a pretty aggressive hydraulic profile. This would respond well to adding the throttle bodies later and you can save the porting work 'til last.

 

The first increment would be ~1500 quid for Supersport performance and the exhaust.

[Peter Carmichael]

That might give you three increments of 135bhp, 155bhp and 170bhp. Somewhere along the way you will want to get a light flywheel, close ratio gearbox (or six speed) an Apollo tank and upgraded suspension and brakes and a limited slip differential.

 

It is well worth getting the gearbox and flywheel sorted out earlier rather than later. This is a game that will keep you happy (and poor) for many years to come.

[Buda]

Cheers, think I've got some more thinking to do but will investigate exhausts.

Does changing exhaust invalidate all the Caterham Warranty or just a bit of it - they must have spent at least a grand sorting mine out in the last 3 months, arn't they nice.

 

Is there a good book one can purchase that would aid my understanding of engine tuning or is just one of those things you pick up as you go along? - I've learn't more off you guys in the past 3 months than over the last 15 years!

 

Anyway off to polish the rabbit and porn the dog to pay for all this!

[Peter Carmichael]

Caterham's own competition 4-1 exhaust is not going to void any warranties.

[Bricol]

What about the sort of thing mentioned in CCC by Dave Walker a few months ago - std cams & head, new ECU and TBs giving up to 160 bhp with suitable exhaust?

 

If remember, he actually said that modifying the head and wilder cams seemed to make it worse (relatively).

 

I would like to go the upgrade route soon - already have a 4-1 manifold waiting to go on - just considering the next steps.

 

 

Bri

[Andy Best]

Buda as you know my cars similar spec to yours and I'm thinking of a similar upgrade route. I figure that the starting point is the Emerald 32 bit ECU, does anybody have experince of or can recommend a distributor in the North West. It would also be good if there's someone to show/teach how to set these things up - anybody good at night classes?

 

Andy

[Red SLR]

Where are you in the North West?

 

X777CAT

[Buda]

I'm in St Helens, Mersey side district bit of club. After a bit of thought I may save my money and upgrade to 1800 supersport as one conversion by changing the p an downy thingies and the bottom round and roundy bit, I may also change some of the squirty squirty sucky sucky bits

[Red SLR]

I will e-mail you offline.

 

X777CAT