Power, or lack of

[square-eyes]

Griff 400 been on dyno and somewhat disappointed with the results, but not surprised. Gas flowed variant so theoretically 250bhp however only found 178 of them.

OK so TVR may have gone ott with the specs but still way down on what i'd like to see.

In terms of how it runs, well from the dyno results you can see the power and torques are smooth and that is how it performs however it is pinking from mid to top revs.

I'm no expert but it appears that the A/F ratio is 'upside down'? 12 ish at bottom end increasing to 14 as the revs rise appears to be the opposite to what i've seen on other posts.

Any advice please??

[The Lukas]

Worn camshaft? They tend to go through them I think. Has it had a replacement?

Edited by The Lukas on Thursday 23 July 23:42

[Vixpy1]

Its way way too lean, will prob go some way to explaining your lack of power, and also the pinking. Did the dyno operator not say anything?

[square-eyes]

All he said was that the A/F curve looked upside down

[Vixpy1]

Which RR was this done at?

[square-eyes]

The Lukas said:

Worn camshaft? They tend to go through them I think. Has it had a replacement?

Edited by The Lukas on Thursday 23 July 23:42

That is what i was thinking and i'm planning to take the sump off to have a quick look. I have a lot of receipts, none of which are for a cam replacement. It has 40k on the clock.

[Vixpy1]

I'm not going to go with camshaft, though it is a possibility.

Check air flow meter, pump, filter and ecu, basically anything fuel related. If you can get the AFR down to what it should be 12 to 13:1 then your power should return.

I'm quite frankly amazed the dyno operator did not tell you this.

[square-eyes]

Vixpy1 said:

Which RR was this done at?

I took it to scoobyworks who are close by however they specialise in scoobies as you can probably guess! It was a Dyno Dynamics RR.

I only really did this out of curiosity and out of convenience and am now looking for the guidance on the next steps ..... the question is can it be improved with tweaks or does it need more significant work?

[Gadgeroonie]

you are looking at wheel power not fly power

did they give you any more graphs ?

[Hoover.]

I'm with Vixpy... I doubt it is the cam, the precat cams tend to last longer then the 500's

[350Matt]

fuel pressure check first , with engine running, this will show if the fuel delivery side is OK

[square-eyes]

Vixpy1 said:

I'm not going to go with camshaft, though it is a possibility.

Check air flow meter, pump, filter and ecu, basically anything fuel related. If you can get the AFR down to what it should be 12 to 13:1 then your power should return.

I'm quite frankly amazed the dyno operator did not tell you this.

To be fair to them, I called up late one afternoon and asked if they could fit me in which they did. I only paid £50 so I wasn't expecting much more.

As far as your suggestions go on fault finding, where is a good place to start to begin to understanding how to diagnose the problem. I have the bible and the Rover V8 overhaul manual, neither of which are been much help with this issue. Are there any recommended reads? cheers

[Del 203]

Do you have any roughness on constant throttle through the rev range ?

I would go with Chaz on AFM, Filters, Pump....

[v8 racing]

Am i missing the obvious here? why dont the power figures cross, at 5500 rpm by the torque it should be making 228bhp, its almost like the torque is at the flywheel and the bhp is corrected down to the wheels? and i would definetly be looking at a poorly air flow meter

Edited by v8 racing on Friday 24th July 08:55

[square-eyes]

Gadgeroonie said:

you are looking at wheel power not fly power

did they give you any more graphs ?

This is all I got. I asked whether it was wheel or flywheel and he said flywheel. Seems to be backed up by the torque axis stating flywheel torque.

[square-eyes]

v8 racing said:

Am i missing the obvious here? why dont the power figures cross, at 5500 rpm by the torque it should be making 228bhp, its almost like the torque is at the flywheel and the bhp is corrected down to the wheels? and i would definetly be looking at a poorly air flow meter

Edited by v8 racing on Friday 24th July 08:55

I spotted that at about 1am this morning but thought i was being daft. I was confused as I thought that the power was calculated from the torque therefore it couldn't be an error ..... just thought my brain needed some sleep.

[v8 racing]

square-eyes said:

v8 racing said:

Am i missing the obvious here? why dont the power figures cross, at 5500 rpm by the torque it should be making 228bhp, its almost like the torque is at the flywheel and the bhp is corrected down to the wheels? and i would definetly be looking at a poorly air flow meter

Edited by v8 racing on Friday 24th July 08:55

I spotted that at about 1am this morning but thought i was being daft. I was confused as I thought that the power was calculated from the torque therefore it couldn't be an error ..... just thought my brain needed some sleep.

Your dead right, by my calculations your car is making around 230 at the flywheel, add to that the loss you are getting from the mixture not being right and i would say you have a pretty healthy motor there

[Vixpy1]

v8 racing said:

square-eyes said:

v8 racing said:

Am i missing the obvious here? why dont the power figures cross, at 5500 rpm by the torque it should be making 228bhp, its almost like the torque is at the flywheel and the bhp is corrected down to the wheels? and i would definetly be looking at a poorly air flow meter

Edited by v8 racing on Friday 24th July 08:55

I spotted that at about 1am this morning but thought i was being daft. I was confused as I thought that the power was calculated from the torque therefore it couldn't be an error ..... just thought my brain needed some sleep.

Your dead right, by my calculations your car is making around 230 at the flywheel, add to that the loss you are getting from the mixture not being right and i would say you have a pretty healthy motor there

Yes, I failed to notice this last night too, its a wheel hp graph vs flywheel torque.

[square-eyes]

that looks better! cheers guys

just a/f to investigate

Edited by square-eyes on Friday 24th July 10:22

[square-eyes]

As for the A/F ratio, i've just done a quick check of the voltages listed in Steve Heath's book and everything looks fine through the revs. Assuming i've done it correctly; checked the readings across the blue and red leads on the left of the connector opposed to the brown and red on the right?

Is that enough to eliminate the AFM as a culprit?

I've not done anything with the fuel system yet other than have a nosey about. I have noticed that when the engine is running, if you listen to the fuel tank there is a kind of cracking noise. It appears to be coming from the upper right of the tank. I've not pulled any of the carpet off but i understand this is where the sender unit it. I am lost as to what the noise may be.