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Frequently Asked Questions - Which Kit?
 
Results from our TP208bhp kit
Fuel injection or Carburettors
Difference in bhp from carburettor kits and fuel injection kits
 
Results from our TP208bhp kit
Question: I been browsing many places for throttle body kits for a c20xe engine, your site is the only one that is very informative so i guess you know what your doing so I’m after a bit of advice. If I fit this kit to a standard rebuilt engine new rings etc and everything is up to standard, will fitting this kit and exhaust give the 208bhp or is this 208bhp an achievable figure with the addition of cams and port matching and lightening and balancing. If this is the case what am i likely to see with just fitting the exhaust and throttle bodies to a standard engine?

Answer: The results we have obtained for the TP208 kit were based on using a standard engine which was in good mechanical condition. It had probably done about 10,000 miles, so it was fully run in. The engine was then placed on a dyno at Griffin Motorsport. The figures were recorded using the engine with no alternator and were corrected using the American SAE system (this usually gives a higher reading than European DIN figures). Apart from the kit and the exhaust manifold and a large bore exhaust system with a silencer, no other modifications have been carried out on the engine. We have run several of the engine kits on the dyno. The lowest reading we have seen was 200bhp and the highest reading for this kit was 210bhp. Obviously, engines do vary slightly and if you were to test the figures on a rolling road or dyno, using a different correction system you are likely to get a different result.

As far as I know, all the customers who have bought this kit or any of the similar kits, have found it totally transforms the way the engine drives and unless you have made other changes to the engine, or your engine is not as in good working condition as you had hoped, there would be no need for any reprogramming to be carried out.

Links: 2.0L Taper throttle body kit

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Fuel injection or Carburettors
Question: I have just bought a standard XE engine and plan to strip it completely and re-build it. Initially I plan to tune it to approx 180-200bhp, to keep costs down. I want to tune the engine further as time & funds allow. Would you recommend for my initial spec carbs or injection?

Answer: I would always recommend fuel injection over carbs. For example you are looking for between 180 - 200bhp, whereas a standard engine on carbs would produce in the region of 180bhp. A standard engine on tapered throttle bodies would produce 200 - 210bhp. With the advantage of improved response and driveability, not to mention’ very good fuel economy. You also mention that you are considering stripping the engine down completely. I know a lot of the XE engines have been around for a long time now, but if your engine is in good condition we have seen many engines tuned to at least the TP208 kit well into the 100,000 mile range. When you fit the kit it comes with up-rated rod bolts, the main area, which would determine the condition of the engine is the big end bearings. which can be inspected whilst fitting the rod bolts. The other reason I suggest the engine is left intact, is that once you start to disassemble the engine, there are many components which may be still in reasonable condition, but once the engine is stripped, should be replaced just because you have gone this far.
The TP 208 kit is fully programmed and does not need taking to a rolling road. If you go to the set up section, you can download a full instruction sheet on how to assemble the kit and this gives you a better idea of what the system looks like.

Links: 2.0L Taper throttle body kit | Instruction Sheet

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Difference in bhp from carburettor kits and fuel injection kits
Question: I’m trying to get some confirmation on the seemingly massive difference between your carburettor and throttle-body kits for this engine. You’re claiming 140bhp from the basic carburettor kit with no internal modifications and you’re claiming 164bhp from the taper kit also with no internal modifications. It seems to me that a set of 40mm dhla's will flow very similar amounts of air to a set of 40mm throttle bodies and peak power appears to occur in the same place so why the 25bhp difference in performance? I’d also like to know if there’s is any major differences between the taper kits and the "multi-throttle" kits which look more like a set of carburettors than the much shorter taper bodies?

Answer: In theory you are correct, you should be able to get the same amount of air through a carburettor and you could do through a throttle body of a similar size. There are any reasons why in reality it does not work quite as you would expect. One of the simplest being, that if you fitted a choke size to your carburettor the same as a throttle body you may well be able to get fairly close, but when you are not trying to achieve peak bhp the gas speed is slower. A fuel injection system is programmed to supply the fuel as the engine requires, whereas a carburettor can only supply the fuel that the vacuum of the engine can draw through it. This is why carburettors have different choke sizes fitted. You have to compromise on peak power over power through the entire rev range. There are many other reasons that come into play, i could literally spend days describing some of the tests we have carried out over many years.

One of the tests we carried out was to take a standard 2.0L XE engine, and place it on the dyno, we initially ran the engine on carburettors and optimised the settings, we gained to sets of results. An engine that was drivable throughout the entire rev range obtained approx 180bhp. We experimented with much larger choke sizes to see what could be achieved, we managed to push the horsepower up to 190bhp but the engine was completely undriveable on anything other than peak rpm. We then took off the carburettors and fitted multi-throttles, the engine instantly produced 195bhp and was even more drivable than the carburettored engine using the smaller chokes. After carrying out all the tests on multi-throttles, we then changed to taper throttles, we managed to produce 208bhp, the engine had slightly more bottom end torque than the multi-throttles, a small increase in the mid-range torque and the torque hung on much longer up the rev range, which was why it produced 208bhp.

On each of the systems we tested, we found it necessary to optimize the exhaust manifolds as well, as each system had a slight variation in its requirements to produce it's best.

One last thing, we have over the years experimented with various engine specifications and have never found that even if an engine does produce, lets say 20 horsepower more than another but over a very small power band, that the engine with the wide power band makes the car quicker round the track.

I would suggest you read an article on our web site about the advantages of Taper throttles over Parallel throttles, which i hope will help answer your questions.

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