MGF CVT fuel injectors

[ashcapri28]

Hello all.

I have MGF CVT W plate

Car runs very well just passed MOT yesterday for third time no advisers

When the MOT inspector did the emissions he notified me that there seems to be air in the system giving the Lambada Reading close to the maximum allowable amount.

The CO 0.04 max allowed 0.30

The HO 18 max allowed 200

Lambda 1.026. max allowed 1.090

If example the inlet manifold gasket had a slight leak it will allow unmetered air into the engine weakening the mixture therefore Rising the figure given for the Lambada Reading.

My question is we all know the plastic inlet manifolds are a weak points so I'm upgrading to an aluminium manifold from a 135 MGTF I'm aware that that they do not have a air temperature sensor that is separate and I'll have to rewire it but that is fine. But I was wondering whether I should upgrade my fuel injectors from the black Type to the blue type. From what I understood the black Type are rated for around 121 horsepower using 90% of the fuel injectors capacity.

As I have a performance exhaust K&N style cone filter cold air feed 52mm throttle body surely the stock injectors would be insufficient so I was wondering if I upgrade into the Blue fuel injectors would make a difference or worthwhile

flow rates are

black injectors are 176 CC
Blue injectors are around 195 CC

The above is approximate I could be a couple out here all there

From my understanding on a test that was done using a rolling road a K&N style filter setup cold air feed etc, increaseses horsepower by 8 on mpi and 12 on a VVC due to the restrictive air box and tubing.

With this in mind having all things being equal with the car producing when new 118 and let's say I've got 125 that would make my fuel injectors are insufficient.

As I'm changing the inlet manifold now would be the time to change the fuel injectors is it worth doing would I upset the ECU I haven't slightly larger fuel injectors?

Comments and opinions invited.

P.s. I'm very well aware of the restrictions for the CVT gearbox nevertheless there was quite substantial improvements when I've done the above modifications also my compression ratio is very high 40 PSI on each cylinder higher then I believe it should be.
This was confirmed from a performance point of view when I continuously get a 0 to 62 time of 8.6 seconds. Manual gear change Using GPS on phone not necessarily 100% reliable method but close to 2 seconds off off book 0 to 62 of 10.5 to 62. When I did exactly the same test in exactly the same circumstances in my VVC MGF with the same modifications although the rear silencer was different but steel stainless steel performance type I was getting 0 to 62 of around 9 Plus seconds car has done 90000 miles tons of owners so possibly the engine was knackered as it's supposed to do 0 to 62 in 7.6 seconds 0 to 60 in 7.
0 to 60 is a crafty way to make a car seem quicker than it really is as due to gear ratios the majority of cars of similar type require 3rd Gear to get to 62 mph.

As a side note when you do these daft tests out of curiosity you have to drive way past the speed you're trying to achieve going by your dials in the car as they can be around 5 miles an hour out at 60 miles an hour.

[talkingcars]

I don't think it is hard to swap the injectors so it might be worth trying them and testing them yourself.
However, and I might be wrong, but I thought the blue injectors were smaller than the black and blue ones.

Also what compression are you getting?

[ashcapri28]

Compression I'm getting is 240-245 psi I think across all four cylinders. I've also had a camera down the spark plug holes and the tops of the pistons and combustion chamber is lovely and clean, so I don't believe it's because of a buildup of carbon the car mileage was about 40000 head gasket was done at 26000 at a cost of £3,000 total, MG specialist in London

[ashcapri28]

The fuel injectors I've got currently in my car are totally black the ones that I've got what with the the alloy head from the the 135 TF are all dark blue ( TARDIS blue)

According to the information I've researched the blue have a slightly higher fuel rate. about 10%

As far as I'm aware the only other alternative is a beige colour which is fitted to the early VVC which is of a greater flow rate over 200cc.

But like you say because the alloy manifold splits in half it might be the case of suck it and see

[Mykel]

When I swapped the plastic manifold for an alloy one on my Steppy I reused the original black ones. They are fine up to 120 bhp, and everything was fine under driving.

The only issue I encountered was an occasional erratic idle when stopping at traffic lights after a short period on overrun, the engine went into a kind of oscillating tickover between 800-1200-ish revs. This may have been down to the slightly larger volume of the plenum. A quick push of the throttle pedal would cure that instantly.

If I were you, I’d give the blue ones a try, the ecu will be able to adapt to the higher flow.

[ashcapri28]

yes I think I may try them.

I do not know the history of these blue fuel injectors that came with the manifold mileage etc. What's the best way to check operational condition and how do I clean them I've seen these spray cans that you can fix to them how good are they? or am I better off sending them to be professionally cleaned but at greater cost?

[Rob Bell]

Hi Ash,

I don't think you really have a problem. The emissions all look absolutely fine and I would not be worried at this point.

The plastic manifold is also a nice piece of engineering. They don't conduct much heat, they don't generally warp and the only issue I've heard of is when a plastic inlet manifold split under turbo pressure (which was very hard to diagnose!) The only issue relates to the inlet manifold gasket - and since these were upgraded from the black to green compound, they rarely cause problems. And if they do leak, it's easy to replace.

Your CVT is a relatively early one - with the IAT separate from the MAP sensor. Later engines have a combined IAT/MAP sensor (different design of manifold too). Swapping over to a later alloy inlet manifold can be done, but you'll need to work out how to get an IAT signal. It may involve you tapping into the alloy inlet manfold to screw in the sensor currently in the car. You should use the car's current MAP sensor (it won't be plug and play to the sensor you are likely to find installed in the replacement TF135 manifold).

For me, I am not sure that the work is worth the effort if the simple goal is to replace a good inlet manifold with an alloy one that you perceive as being more reliable. But if you are thinking about other advantages, or fancy the challenge, then go for it

[ashcapri28]

Hi Rob the problem is although the CO and HO are fine on the emissions report the Lambada sensor is reading high, higher than it was last year and the previous year before that over the years its progressively given a higher Reading. The MOT tester seem to think there's excessive air in the system which is why it's giving a higher Reading yes it still passed the MOT emissions but only just so my concern is why is the Lambada reading high even if it is within specification , it took him the third attempt to get this pass reading the first two attempts were fails I took the car out for a blast as well so the cat was nice and hot and then straight into the MOT testing Bay. I have wondered also if the Lambada sensor itself could be on the way out I do have a replacement sensor but would need to replace the manifold at the same time as the likelihood is after 20-years the sensor will be fused solid to the manifold and is unlikely to come out easily.

What I don't want to do is to leave it as it did actually pass and then next year it refuses to pass and fails and then be without my car until it's fixed

[ashcapri28]

Why can't I use the duel iat-map sensor on the alloy manifold. I would obviously replace it with a brand new item and like you say it's a combined sensor therefore why can't I take the wiring from the original iat sensor and wire into the dual iat - map sensor?

[ashcapri28]

As the Lambada sensor is the only sensor I haven't changed on the car this is going to be changed first along with a new manifold. Which brings me to my next question eBay list stainless steel copies of the original manifold for around £150 but there are two options a full bolt and a 6 Bolt just the same as the original exhaust systems but I was wondering which one should I buy I know the car that I have originally has the full bowl but if you're replacing the whole thing it shouldn't matter which one you buy as they are both effectively the same item in terms of their fitted but I was wondering if there's any benefit of having the six bolted type?

[ashcapri28]

Typos in that last message.

4 bolt and 6 bolt

[Mykel]

The 6 bolt is for Euro 3 exhausts, which use a different location for the lambda sensor (in the flexi pipe, not the manifold). Also, you will need a different kind of heat shield.

[talkingcars]

IMHO the 6 bolt version has longer smoother bends so should flow better and as the lambda probe is further from the exhaust ports so should run cooler.
I continued to use the old heat shield when I swapped.

[Rob Bell]

Hi Rob the problem is although the CO and HO are fine on the emissions report the Lambada sensor is reading high, higher than it was last year and the previous year before that over the years its progressively given a higher Reading. The MOT tester seem to think there's excessive air in the system which is why it's giving a higher Reading yes it still passed the MOT emissions but only just so my concern is why is the Lambada reading high even if it is within specification , it took him the third attempt to get this pass reading the first two attempts were fails I took the car out for a blast as well so the cat was nice and hot and then straight into the MOT testing Bay. I have wondered also if the Lambada sensor itself could be on the way out I do have a replacement sensor but would need to replace the manifold at the same time as the likelihood is after 20-years the sensor will be fused solid to the manifold and is unlikely to come out easily.

What I don't want to do is to leave it as it did actually pass and then next year it refuses to pass and fails and then be without my car until it's fixed

It's unlikely the inlet manifold causing the problem. More likely a leak in the exhaust manifold ahead of the Lambda.

The numbers still aren't a concern. Also, Lambda values tend to creep up over time when they start failing, but my guess is your exhaust manifold is also likely to be fine. Common things to look for would be a blowing gasket - either between the head and header, or between the header and down pipe. Or there may be a crack in the header, perhaps at a weld as the 4 header pipes merge.

But I reckon it'll likely be the Lambda sensor itself. If you have access to Live data and can record the telemetry (the pscan will do this), then you can look at the oscillation pattern of the Lambda to get a clearer idea of what is going on.

My only word of caution is about replacing stuff that may not be related to a problem that is not yet a problem

[Rob Bell]

Why can't I use the duel iat-map sensor on the alloy manifold. I would obviously replace it with a brand new item and like you say it's a combined sensor therefore why can't I take the wiring from the original iat sensor and wire into the dual iat - map sensor?

If you can find a new alloy inlet manifold with separate temperature and MAP sensors, then yes, that'll do nicely.

[Rob Bell]

As the Lambada sensor is the only sensor I haven't changed on the car this is going to be changed first along with a new manifold. Which brings me to my next question eBay list stainless steel copies of the original manifold for around £150 but there are two options a full bolt and a 6 Bolt just the same as the original exhaust systems but I was wondering which one should I buy I know the car that I have originally has the full bowl but if you're replacing the whole thing it shouldn't matter which one you buy as they are both effectively the same item in terms of their fitted but I was wondering if there's any benefit of having the six bolted type?

Your "T" reg is likely a 4-bolt, but may be very close to the change over from EU2 to EU3. Best check what you have or else buy both the manifold and down pipe together which will solve that concern instantly

[ashcapri28]

Yes I've already decided to replace the manifold downpipe together I already have a Lambada sensor. I will then take the car for an emissions test and go from there

[ashcapri28]

The Lambada sensor is original to the car and so 20 years old with 48000 miles on it so it could do with changing