[scottyf]

Less restrictions in the exhaust will always make a difference.

 

[Shimmerydolmeo]

Less restrictions in the exhaust will always make a difference.

Just ordered a set for my top end rebuild, clutch, quaife, cambelt, radiator. Getting sexy red plenum\rocker and air intake. Will take 3-4 wks but will post some pics when done. Given the pressure readings im expecting a big improvement.

 

[Whitlam]

Less restrictions in the exhaust will always make a difference.

Or you would be surprised at what little difference it makes.
Here is some ******* science which is hard to refute.
https://youtu.be/azPKIjxmmdU
I do luv Roadkill :smoker:

 

[MGS]

Not sure that test is a good one. They didn't do the test using a full exhaust system which seems a bit pointless? If you've increased or reduced flow in the manifolds then testing changes in power (gains or reductions) can only be confirmed with the full exhaust system intact (with all the silencers and cats in place). Also the main thing is that even with their version of the test, using only the front section of the exhaust they still saw reductions in power. It would be interesting to see what the difference would have been with the full exhaust system and all the CATs in place.

The key difference with the CF3 3.0 litre and 3.2 engines is the manifold CATs. These are very restrictive and removing these and a remap gives an extra 20-25+ BHP instantly. The difference is pretty significant I can vouch for that!!!

 

[Shimmerydolmeo]

Not sure that test is a good one. They didn't do the test using a full exhaust system which seems a bit pointless? If you've increased or reduced flow in the manifolds then testing changes in power (gains or reductions) can only be confirmed with the full exhaust system intact (with all the silencers and cats in place). Also the main thing is that even with their version of the test, using only the front section of the exhaust they still saw reductions in power. It would be interesting to see what the difference would have been with the full exhaust system and all the CATs in place.

The key difference with the CF3 3.0 litre and 3.2 engines is the manifold CATs. These are very restrictive and removing these and a remap gives an extra 20-25+ BHP instantly. The difference is pretty significant I can vouch for that!!!

Can't. Bloody. Wait.

 

[chipt33]

Here is the remap chart. Nice healthy gains (specially torque) but notice the power output line isn't as smooth as I would expect it to be up to 4250 (ish) RMP and this was both prior to the map and after which corresponds to what I'm feeling in power flat spot at around 3000 RPM.

Thanks R.T. injector cleaner is a good shout. Wondering what else I could get looked at if not injectors..

Is the graph 500 revs out of sync?

 

[chipt33]

oops wrong people, sorry.

 

[MGS]

Hi guys, I am restarting this thread as shortly after the apparent resolution of the lack of power/flat spot issue (which was thought was due to an air-leak), the issue came back...

So just to recap the issue is a sudden flat spot when reaching around the 3000-3500 rev range, more noticeable in high gears under load (so an uphill stretch of road). Its on a specific range on the accelerator pedal, best I can describe it is when in between holding the pedal at cruising speeds and just before you push your foot down to open the throttle body open a bit, its right between the two. It feels like it wants to pull away but is being held back.

It is driving me mad especially as the other day when I drove it, the car literally burst forward and I couldn't believe the power, it was like a different car, it lunged forward throughout the rev range and the flat spot was gone. Next time I turned it on it was back to having the flat spot...

I've just had the fuel pump replaced as was told the fuel pressure reading was fluctuating at half throttle and it feels like the power is there under full throttle but still has this flat spot at half throttle. Lambda sensors checked ok, plugs replaced, CAT checked ok, fuel pump replaced, MAF replaced (genuine Bosch) showing no error messages. If anyone has any ideas please help its driving me mad!!!!!

 

[Firstcaralfa]

I was going to go with MAF at that kind of rev range, but as you say it has been checked.

Isn't hesitation at around 3/4K a known issue with the 3.2? I could be making that up entirely but something tells me it is!

Also do you mind me asking where you got your rebuild?

 

[MGS]

I was going to go with MAF at that kind of rev range, but as you say it has been checked.

Isn't hesitation at around 3/4K a known issue with the 3.2? I could be making that up entirely but something tells me it is!

Also do you mind me asking where you got your rebuild?

Firstcaralfa thanks for taking time to reply. I haven't had a rebuild on the car, just lots of other bits done due to being obsessed with her! All the work on my car is carried out by Alfa main dealer or specialist.

Yes MAF replaced and I'm not aware of any known problems with hesitation with the 3.2 GTs. The main issues is that the other day very randomly it drove without the flat spot and it was like a different car it felt 'unleashed' with all its horses on full attack mode then the next day back to having a flat spot...(Grrrrrr)....Had the fuel pump replaced since and it feels like t he power is there now but the flat spot in that rev range is still there.

I've ordered some recommended injector cleaner which will be my next step, if no good back into Alfa she goes as want to get her 100%.

 

[GavinH]

Hi MGS, it's certainly very frustrating to have an intermittent problem like that.

If you have a new MAF already, next thing I would look personally at is the lambda sensor. I know it's been tested as ok, but it's one of those things that seems to go gradually and loses efficiency with miles, even though it won't throw up a fault code. It's a consumable unfortunately, a bit like a spark plugs.

For the injectors, I'd suggest not bothering with fuel additives - just take them out and get them cleaned & reconditioned. Even if this is not causing the hesitation problem you will notice a difference in performance if the engine has fairly high miles.

best of luck,
Gav.

 

[MGS]

Hi MGS, it's certainly very frustrating to have an intermittent problem like that.

If you have a new MAF already, next thing I would look personally at is the lambda sensor. I know it's been tested as ok, but it's one of those things that seems to go gradually and loses efficiency with miles, even though it won't throw up a fault code. It's a consumable unfortunately, a bit like a spark plugs.

For the injectors, I'd suggest not bothering with fuel additives - just take them out and get them cleaned & reconditioned. Even if this is not causing the hesitation problem you will notice a difference in performance if the engine has fairly high miles.

best of luck,
Gav.

Thanks GavinH appreciate the response. Yes frustrating to say the least, all my friends think I'm nuts as they think my GT is severely rapid but I just know somethings not quite running right so need to get it resolved. The Lambdas were properly tested and had the outputs charted and they were performing well within their normal tolerances so I'm reluctant to throw money at these however completely agree the injectors sound like the next step, but not sure the amount of hours work this normally entails.

I'll keep everyone posted in case anyone has a similar problem.

 

[GavinH]

The 3.2 has 3 (or is it 4?) lamba sensors doesn't it so not a cheap approach to replace those as you say.

Regarding the injectors, to be honest, I'm not at all sure if a bad injector would lead to the sort of flat spot you describe. I just meant that taking them off to clean & recondition would be more effective than fuel additive (but additive should do no harm).

I see you have it remapped, was the problem there before you got that done? Did they give you a chart of the air/fuel ratio.

 

[Firstcaralfa]

Firstcaralfa thanks for taking time to reply. I haven't had a rebuild on the car, just lots of other bits done due to being obsessed with her! All the work on my car is carried out by Alfa main dealer or specialist.

Yes MAF replaced and I'm not aware of any known problems with hesitation with the 3.2 GTs. The main issues is that the other day very randomly it drove without the flat spot and it was like a different car it felt 'unleashed' with all its horses on full attack mode then the next day back to having a flat spot...(Grrrrrr)....Had the fuel pump replaced since and it feels like t he power is there now but the flat spot in that rev range is still there.

I've ordered some recommended injector cleaner which will be my next step, if no good back into Alfa she goes as want to get her 100%.

Sorry I thought I read that you had a top end rebuild of the engine!

 

[MGS]

The 3.2 has 3 (or is it 4?) lamba sensors doesn't it so not a cheap approach to replace those as you say.

Regarding the injectors, to be honest, I'm not at all sure if a bad injector would lead to the sort of flat spot you describe. I just meant that taking them off to clean & recondition would be more effective than fuel additive (but additive should do no harm).

I see you have it remapped, was the problem there before you got that done? Did they give you a chart of the air/fuel ratio.

Yes the problem was there before the map and I didn't get the fuel air ratio but the mappers said that the map didn't show a smooth curve like they would expect. We thought we'd cracked it as the plenum chamber had an air-leak but the problem came back.

I've just this minute found a symptom which I can replicate every time.

Any gear at any speed, if I accelerate up to around 5000 RPM, then lift foot completely off accelerator pedal the revs drop smoothly down to about 3500 RPM and at point it feels like someone has put the brakes on (not literally but in terms of sudden drop in power).

The engine almost feels like it chokes itself or a restrictor is turned on to the point where you notice the massive power drop. The 3500 RPM rev range is where I also feel the flat spot going up the rev range but its more subtle.

Could this be throttle body related???

 

[MGS]

Sorry I thought I read that you had a top end rebuild of the engine!

No worries, with the amount of work I've had done to her it was an easy mistake to make!

 

[GavinH]

It almost sounds like there's fuel (or maybe air) starvation at a certain point in the rev range. Unfortunately there's a lot of things that can put that out of sync. I presume you've checked the basic stuff - blockage in air filter, cracks in the air intake?
It sounds like the sort of thing you get with a bad MAF but the swap would seem to discount that possibility...
Does the flat spot occur on full or partial throttle when accelerating? If it goes away on full throttle that might point towards a bad lambda sensor.
Ultimately though, the best advice I can give is to take the car to an Alfa specialist and get them to take a look..throwing parts at the problem will get expensive unfortunately!

 

[Aramis]

Could be your air intake and manifold that was modified. Try putting back the original Alfa intake hose with the little box attached, apparently it stores extra air when the engine cannot get extra from the hose itself.

Love my GT

 

[MGS]

It almost sounds like there's fuel (or maybe air) starvation at a certain point in the rev range. Unfortunately there's a lot of things that can put that out of sync. I presume you've checked the basic stuff - blockage in air filter, cracks in the air intake?
It sounds like the sort of thing you get with a bad MAF but the swap would seem to discount that possibility...
Does the flat spot occur on full or partial throttle when accelerating? If it goes away on full throttle that might point towards a bad lambda sensor.
Ultimately though, the best advice I can give is to take the car to an Alfa specialist and get them to take a look..throwing parts at the problem will get expensive unfortunately!

Thanks gavinh, its most noticeable at part throttle around 3000-3500 rpm where it feels like its being held back but its pretty flat right up to 4500 rpm. It does pick up at this range but then I know the busso engine gives extra oomph at this point anyway. It definitely feels much more flat and laboured than my old GTV V6.

Aramis thank you, I'll suggest that to the specialist its going in next week!

 

[chipt33]

any one sussed the graph yet?