Questions about my Emerald-managed RV8 power graph

[domV8]

Hi Guys,

After having ongoing problems with my TVR wiring, I have had the OE dizzy/14CUX removed and replaced by an Emerald ecu.

The mapping has made the car much smoother down low, and reduced (although not removed) the shunting issues - but I have not "floored it" yet...

It achieved 295BHP with ~325lb/ft - the RR graph shows the power delivery:



I am quite surpised with the drop-off in torque (therefore power) from around 5000/5100 - and was wondering whether people had any suggestions.

The engine is a rebuilt 4.6l (covered ~3000miles) with the following modifications (summarised):

- Emerald running coilpacks
- TVR885 cam
- TVR Big Valve Heads
- JP Exhausts SS manifolds
- JP Exhausts Y-piece (inc. 200cell hi-flow cat)
- JP Exhausts SS swan neck
- Bosch "red top" injectors
- ACT smooth-bore intake hose & 90-degree elbow
- AFM removed
- SC plenum spacer & thermal insulator gasket

...although it is running the OE plenum, intake manifold and trumpets.

However, as you can see, the torque drops off quite quickly at a much lower RPM than I would have expected - bearing in mind the cam, BV heads, etc.

When I spoke to Dom at TVR Power about the TVR885 cam, he said the cams operating range was up to about ~6200 with a drop-off at that point - but as you can see, the torque/power in mine is dropping off much earlier than that. I have had the cam timing checked, and it is correct...

My gut feel is that either this may be something to do with:

1. the plenum, trumpets, or intake restricting flow
2. the engine still being "tight" (~3000miles), and requiring more use to "loosen up"
3. Some "wave pulse reflection ram-effect" thingy that has changed due to the addition of the plenum spacer
4. Any combination of the above...

...but wondered if you guys had any other suggestions or opinions?

Feel free to ask any other details...



Thanks,


Dom

Edited by domV8 on Friday 9th July 13:03

[sgrimshaw]

Do you have a "before" run, ie before you replaced the 14CUX/Dizzy?

[bigdods]

cant help with any ideas but would be interested to know if thats at the wheels or the calculated fly figure? I assume its calculated and if thats the case it looks a bit down on power for that config. You are right I think to be concerned about how early the torque drops off. Mine certainly starts a very slow decline from ~5100 but doesnt start to drop sharply until ~5700

The calculated figure for my 450 is 268.1 BHP (which I think is very optimistic) , its a standard setup with only an ACT induction pipe and pre-cats removed.

Hopefully someone who actually knows what they are talking about will be along soon with some real advice !

Edited by bigdods on Friday 9th July 11:22

[domV8]

sgrimshaw said:

Do you have a "before" run, ie before you replaced the 14CUX/Dizzy?

Unfortunately not, the engine was rebuilt and run-in with the dizzy - but had not been set-up on the RR at that point, and I know that the ignition advance was very conservative at that point anyway - so would not be a "fair" comparison.

bigdods said:

cant help with any ideas but would be interested to know if thats at the wheels or the calculated fly figure? I assume its calculated and if thats the case it looks a bit down on power for that config. You are right I think to be concerned about how early the torque drops off. Mine certainly starts a very slow decline from ~5100 but doesnt start to drop sharply until ~5700

The power shown is at the flywheel. Forgot to say, pre-cats removed on mine too...

Dom

[Pupp]

Looks a nice smooth graph/distribution but would be interesting to see the AFR plot for the run. Assuming the cam is timed as it should be, I'd say the roll off may well be due to intake restrictions if by 'OE trumpets' you mean 38mm ones of stock length. Can't really expect the best from big valve heads and other goodies etc with those and a stock inlet manifold upstream, although that's a healthy enough torque figure and high gas speed/resulting swirl from smaller passages can be good for torgue

[350Matt]

Without a doubt go shorter and larger on the trumpets a 45mm Ø tapered inlet port will transform it, you don't have to worry about the carbon ones an ally set form ACT will do and then broddle out the inlet manifold to match

[clive f]

I`d say cam timing, it only needs to be a degree or two out to shove the torque and bhp curves around.


I found this out for myself once

[spend]

clive f said:

I found this out for myself once

You needed some convincing IIRC

[domV8]

clive f said:

I`d say cam timing, it only needs to be a degree or two out to shove the torque and bhp curves around.

I thought this too Clive - but I have had it checked twice now, once at a local garage, and then prior to the RR mapping - and on both occasions the timing was as Dom TVR Power has stipulated...

Dom

[clive f]

domV8 said:

clive f said:

I`d say cam timing, it only needs to be a degree or two out to shove the torque and bhp curves around.

I thought this too Clive - but I have had it checked twice now, once at a local garage, and then prior to the RR mapping - and on both occasions the timing was as Dom TVR Power has stipulated...

Dom

I`d definately take 350matts advice and play with trumpets then mate.

[spend]

If its got one of the crap 400 inlet manifold & trumpet bases, its a lot of work over just fettling trumpets, and something like £600 for the enlarged set of manifold+base+plenum....

Putting wider trumpets in the 38mm setup isn't really going to help very much IMHO.

[domV8]

Whats the diameter of the 500 intake manifold runners and trumpets..?

Dom

[spend]

@45mm as said above.

[domV8]

Sorry!
Seem to recall some talk of 42mm trumpets somewhere - wondered which it was...

Thanks,

Dom

[Pupp]

All you need is a decent and torquey drill, a good flexi-drive, a couple of rotary cutters, strong wrists, many hours, a spare good flexi-drive for when the first dies as it tries to kill you when a cutter snags, stronger wrists, more hours, and an old hoover to suck up the swarf (of which there will be much)...oh, and lots of sticking plasters

[big geoff]

Spend why is the 400 manifold crap compaired to others

[spend]

Because you end up with weedy power?

[Vixpy1]

spend said:

Because you end up with weedy power?

And being weedy unpleased

[Simon says]

domV8 said:

Sorry!
Seem to recall some talk of 42mm trumpets somewhere - wondered which it was...

Thanks,

Dom

Those are from the rare dual throttled body plenum SDI set-up (i think) i have a set they also have a larger flare

Edited by Simon says on Saturday 10th July 10:42

[rev-erend]

That's pretty good power / torque for a 4.6..

Looks like the inlet manifold is causing the restriction.

Plenty of good idea's on here :

http://www.mez.co.uk/ms12.html

Adding a set of Wildcat TB's should release the missing horses..

Edited by rev-erend on Sunday 11th July 11:57