Vx with Powerspeed 4:2:1

[Paul Deslandes]

Does anyone have reliable RR plots/results from a 2litre Vx running a 4:2:1 exhaust?

I'm currently on a 4:1 and getting loads of top-end power (250+) but, insurprisingly, short of bottom/mid range torque. So I'm lloking at supplier options for a new exhaust system. Powerspeed seem to be recommended but I would like some quantitative data rather than subjective impressions which are so often clouded by the fact that one has just spent a lot of money, therefore it must be (has to be) good!

 

I need to know that if I go this path and get it mapped by Steve Greenald at R&T that it won't bomb and be no better, or even worse, than what I have now.

 

Thanks

 

 

[Paul Gibb]

Paul,

Swindon recommended 4:2:1 to me and have information on this (and a room full of different spec manifolds for use on their dynos). I had an exhaust made to their spec by Graham Frankland @ EBD. I can send you a copy of the relevant dyno sheet (but will require your email address).

 

 

L7 FUN

[Gambo]

Paul , As i'm running your old cams I can give you a some figures from my rolling road sesion at track& road, I have a SBD 4;2;1 with one of there silencers on. Max power came out at 228bhp at 7500.147lbft at 4000, 162 at 4500 maxed at 178lb f at 5600 and droped off steadily to 170 at 7550 and then 150lb ft at 7800. don't know how that compares to your motor, but both steve sais that they always seemed to have good results with one of SBD's manifolds. If you want to have a chat give me a ring i'll blat mail my number.

I will expect somebody to disagree though

 

RED 2.0 HPC

[F355GTS]

Paul

 

I'm running an EBD 4-2-1, it was mapped with a Techcraft 6", 26" long silencer but now has a 7" Powerspeed silencer, it feels even more powerful with the Powerspeed over the Techcraft.

 

Power plot is here

 

Mark

 

Edited by - F355GTS on 14 Aug 2006 19:54:27

[EFA]

On a VX the most critical metrics in exhaust design are:

 

The port exit velocity - you need primaries as straight and equal in length a possible to ensure efficient pulsing.

 

4:2:1 will offer improved torque over 4:1, but the biggest benefits will be gained through good cam selection.

 

You don't say what the torque figures are, so its hard to judge.

 

K2RUM - The car of two halveswith a hole in the engine

[Paul Deslandes]

Thanks for responses guys.

 

figure are:

RPM Torque BHP

 

2500 113 54

3000 129 74

3500 131 89

4000 136 105

4500 144 123

5000 163 156

5500 166 174

6000 171 196

6500 179 221

7000 176 235

7500 172 246

8000 166 253

8425 151 241

 

Click here

 

to see my power/torque curves. Cams are SBD 220 ex 298 deg and 230 inlet 304 deg. Exhaust is 4:1 with matched primaries but we are severely short of bottom end torque which is a handicap for hill climbs where you can make several slow speed 're- starts' in the course of a run.

 

It has been suggested that I could get another 20 + lbft at the bottom end with a change of exhaust.

 

Does anyone have experience of Powerspeed manifolds as well as their silencers?

 

 

 

Edited by - Paul Deslandes on 14 Aug 2006 12:56:40

 

Edited by - Paul Deslandes on 14 Aug 2006 13:07:39

 

Edited by - Paul Deslandes on 14 Aug 2006 13:11:54

[Paul Deslandes]

Mark

 

That's some power curve - still climbing at 8500! What cams do you have in there?

 

How's the noise with the shorter silencer? I'm sure I'll have to go that route as well and I know you've had problems with noise in the past.

 

I've got three choices:

1) modify my existing system from 4:1 to 4:2:1 but this won't leave much room for a silencer

2) buy an expensive BTB made unit from SBD plus a new silencer.

3) get a whole new system from someone like PowerSpeed or EBD.

 

Paul

 

 

[F355GTS]

Paul

 

Exhaust Cam is a QED 450 item, Inlet is a Piper Race, IIRC 304 degree 12mm lift, can confirm if required. Static Exhaust is 96.5dB at 4.5k revs but was 104db at 5,900 when tested with old silencer at Goodwood last year, I suspect it's maybe 1dB less with the powerspeed. My noise problem is all induction now I've editied my old post as it should say 7" silencer which is still 26" long!

 

Mark