[lsowden12]

Just wondering whether theres a difference between the cams used on the lower horsepower 1.4 k series 200 series engines and the ones on the 103bhp one? I had an engine rebuilt recently after a head gasket failure (not just the gasket replaced, long story) and the car came back slower than before.
Everything from the spark plugs to the entire exhaust system have been swapped out since it returned to no avail, the only logical theory I have now is that there is somehow a difference between the cams and that the donor engine came from a lower bhp model.

Any other ideas are definitely welcome. For context, the car also idles at around 1100 rpm when warm instead of the usual 950. The idle is stable. I don't believe it's the ecu. The inlet used to be alloy but was swapped for plastic for pipe routing reasons but the throttle body is a 52mm one. The alloy is 56mm so the car used to have a 56mm TB but as far as im aware that doesnt matter. I still have the old inlet and throttle body if it does matter. Its a 94 SEI

[itcaptainslow]

Has the cam timing been checked? Prime symptom of it being a tooth or two out.

Either that or the sprockets have been put on the incorrect way around (the roll pins inserted in the “Ex” gap instead of the “In” gap for the inlet cam, for instance) although this usually results in a non-start.

[lsowden12]

Not sure to be honest, I have had the car back for 5 months at this point but have yet to have checked timing because I assumed since it was done very recently it must have been right, can definitely have a look though

[961tat]

I would go back to the alloy inlet and throttle body first ecu will be set up for that and as far as I know the cams are all the same it the throttle body that lowered the bhp on the plastic inlet models they had a restricted on them easy removed but they were not 52mm , sounds like you have modified it all .

[Evil C]

The inlet used to be alloy but was swapped for plastic for pipe routing reasons but the throttle body is a 52mm one. The alloy is 56mm so the car used to have a 56mm TB but as far as im aware that doesnt matter. I still have the old inlet and throttle body if it does matter. Its a 94 SEI

The early 1.4 fitted to the Metro and R8 did have a 56mm throttle body, and later engines switched to a plastic inlet manifold with a 48mm throttle body. I am not quite sure when the change took place (I thought about 1995 when the engine was modified and expanded to include 1.6 and 1.8 versions, but I may be wrong), but it is possible that a 1994 model might even have originally had a plastic inlet manifold and a 48mm throttle body? I am sure someone around here knows for sure

If it had a 56mm tb, and you have now come down to a 52mm, that restriction could well be the cause of the power loss. However, throttle body changes don't always do what you expect; changing the 48mm body for a 52mm was deemed a popular mod for the 25 and ZR with the 103ps version of the K16, but more than one person who put their car on a rolling road actually found that fitting the 52mm tb to the standard manifold actually resulted in a decrease in power because although the throttle aperture was much wider, it upset the flow through the inlet manifold. The 52mm throttle body only seemed beneficial if fitted in conjunction with the VVC alloy inlet manifold and porting the head to match it and preferably a remap.

If you have changed from a 56 to a 52mm throttle body, a remap may serve to rectify the issues.

Not only were the cams the same for both 84ps and 103ps versions of the engine, but both exhaust and inlet cams were identical. The only difference was a restriction in the throttle body, which it is possible to remove, but is far easier to just fit a second hand unrestricted one along with its cable (which is slightly longer than the one for the restricted TB).

[Mr Teddy Bear]

Just to add to the conversation regarding manifolds/throttle bodies:

my very late 93 build 214Si is according to the book a 94 model year build she has the early petrol filter, alloy manifold and obviously the larger T.B and really flies.

The acceleration from 70 upto well in excess of the motorway national speed limit is 'brisk' to say the least. This is with gentle pressure on the pedal, NOT flooring it.

It's an outstanding level of performance from a 1397 cc engine!

My YouTube research suggests that one of the best E5 fuels is to be found at the Tesco pumps!

[lsowden12]

Right see that makes more sense, I was always under the impression that the 56mm throttle body was a waste of time if you already had a 52mm because they performed the same, by the sounds of it that isnt necessarily the case at all. That being said, since it doesnt seem to have been asked before, if a 200 came with the 56mm from factory and it was downgraded to a 52mm, it would be the cause of reduced power? The question has been asked the other way round regarding stepping up from the 52 to a 56 and the general consensus seems to be it doesn't make a difference so I am slightly confused.

It seems like it would be common sense to assume that obviously the power would be reduced if you reduce the size of the TB but I guess with most niche issues with these cars theres never a proper answer because they sometimes work in very strange ways

And yes, the reason I noticed the power was reduced in the first place is because BOY did the car used to fly before the head gasket went, genuinely one of the fastest cars I've owned with such a tiny engine, now its more akin to the speeds of any other random modern economical hatchback on the road

[961tat]

Check the timing again i would .

[Mr Teddy Bear]

The ideal fuel to air ratio for efficient combustion 1:15 parts of air. This would suggest that the ECU is matched to the throttle body, as a smaller T.B passes a smaller volume of air in a given time and there are no carburation issues going on behind the throttle butterfly valve.

[lsowden12]

The ideal fuel to air ratio for efficient combustion 1:15 parts of air. This would suggest that the ECU is matched to the throttle body, as a smaller T.B passes a smaller volume of air in a given time and there are no carburation issues going on behind the throttle butterfly valve.

Makes sense, will check the timing tomorrow to make sure it’s not that but if that fails it’s probably going to end up with an inlet and throttle body swap, just trying to rule everything else out first because it’ll be a relatively time consuming job

Either that or I guess the alternative is to accept that it’s speedy days are over, the fuel economy is absolutely fine and there’s no other issues minus the higher than normal idle so ultimately I feel like I could leave it with no problems