Discussion
Maybe a stupid question but I can't seem to find any answers and the search seems down again.
If I were to fit a twin plenum set-up (have been offered one relatively cheap), would I have to replace the AFM and/or chip or remap the ECU?
Also, I am using a 5ltr trumpet base with the 5 ltr TVR 44mm trumpets at the moment, would I suffer significantly by having to use the wide twin plenum base which only has 42mm trumpets (I believe)?
If I were to fit a twin plenum set-up (have been offered one relatively cheap), would I have to replace the AFM and/or chip or remap the ECU?
Also, I am using a 5ltr trumpet base with the 5 ltr TVR 44mm trumpets at the moment, would I suffer significantly by having to use the wide twin plenum base which only has 42mm trumpets (I believe)?
If the twin plenum has the same throttle pot as the single unit (same sweep in degrees and resistance,) and you retain the stock AFM I dont see an issue with the ECU or chip as the AFM controls the fueling but Ive not tried it. The twin plenums are getting on a bit now, and are prone to letting in air around the throttle spindle that leads to idle issues, so make sure there's no play in the shafts.
estutjaweh said:
Maybe a stupid question but I can't seem to find any answers and the search seems down again.
If I were to fit a twin plenum set-up (have been offered one relatively cheap), would I have to replace the AFM and/or chip or remap the ECU?
Also, I am using a 5ltr trumpet base with the 5 ltr TVR 44mm trumpets at the moment, would I suffer significantly by having to use the wide twin plenum base which only has 42mm trumpets (I believe)?
Have you thought about going for a bored out standard plenum with a 72mm inlet ..Then you could go for the larger trumpets and port match the inlet manifold .If I were to fit a twin plenum set-up (have been offered one relatively cheap), would I have to replace the AFM and/or chip or remap the ECU?
Also, I am using a 5ltr trumpet base with the 5 ltr TVR 44mm trumpets at the moment, would I suffer significantly by having to use the wide twin plenum base which only has 42mm trumpets (I believe)?
Do`n t know of it will make a difference on a 4l
I'm already running the large 5 ltr trumpets (which use a bored out base and manifold).
Cost wise I don't see how the price of a 72mm plenum can be justified when compared to the extra few pounds for a twin set-up. On style alone I would therefore prefer the twin. I also believe the twin system will open up more options for future tuning possibilities but I can't find any comparisons anywhere to confirm this.
Cost wise I don't see how the price of a 72mm plenum can be justified when compared to the extra few pounds for a twin set-up. On style alone I would therefore prefer the twin. I also believe the twin system will open up more options for future tuning possibilities but I can't find any comparisons anywhere to confirm this.
daveparry said:
I have a 72mm bore plenum and have shortened my trumpets, fitted the ACT smooth bore hose and K&N filter, finding a bigger AFM was easy cos they are everywhere, i got mine off of a Jag and yes it does make a difference! probably 20bhp +
Do you know which Jag unit this was? How was wiring it? Relatively easy or....the other type of easy?Not sure how relevant this is but I've just (last few days) gone from a 72mm single plenum to the ACT twin, 45mm J.Eales trumpets in both cases (on a J.Eales 4.6). No idea what the bhp or torque change is but I don't care, the throttle response alone made it well worth doing. For reference the throttle bodies in the twin are Jenvey 52mm. Thing is, you can't quantify throttle response but the FEEL is something like 40bhp+ increase at least. Even though it may only be less than 10. Certainly I wouldn't go back to my single 72mm plenum now.
Im just in the process of getting a digital unit to remap the output of Bosch or Lucas 20AM AFM to match the Lucas 5AM. It may be a much bigger hole, but as the 5 ltr engine already causes the 5AM AFM to reach its full 5 volts before peak power, it would seem a pity to remap a bigger AFM to do the same- but I think you will need to do this if you want to stick with the same fuel map chip. A friend is running around 315BHP with the stock AFM and TVR chip, (working on the basis most 5ltrs are around 270-280 BHP ex factory)so I guess there must still be some scope for improvement with better airflow and without remapping. I thought the Jag unit was the same size as the TVR / Range Rover one - it just lacks the CO trim adjustment.
Edited by blitzracing on Sunday 12th May 21:24
estutjaweh said:
Do you know which Jag unit this was? How was wiring it? Relatively easy or....the other type of easy?
My thoughts, from my own engine. May be wrong, but like London buses, if they are, then three corrections will be along shortly!Just had my plenum changed to 72mm by V8D. It has "3.9" on it, as part of the casting, so my bet is that it is a Rangie or Disco part in my case. Rob is now going to be changing my AFM to a P38 one, as I am maxing out the stock TVR one. and my injectors to Bosch, same reason.
Here you get to the nub of the problem. Go over 285 bhp, and you start maxing out the TVR stock AFM, the injectors etc, and the result is the fuel switches off at that point, you lose power up the top of the rev range, but worst of all, you start running horribly lean (AFR >20) which can break your engine.
I may well sound really stupid, but I'm going to ask anyway. Maxing our at 285bhp, can that be correct? The standard guestimate from TVR was 285BHP from a 450. I kind of thought that some kind of buffer would be built in to most parts so that they could take a tad more.....
Out of I interest, what else would you need to make the most out of something like that? ECU/mapping, MAF, heads etc.
gmw9666 said:
Yum yum, mucho wantage right there Out of I interest, what else would you need to make the most out of something like that? ECU/mapping, MAF, heads etc.ybt1982 said:
I may well sound really stupid, but I'm going to ask anyway. Maxing our at 285bhp, can that be correct? The standard guestimate from TVR was 285BHP from a 450. I kind of thought that some kind of buffer would be built in to most parts so that they could take a tad more.....
Out of I interest, what else would you need to make the most out of something like that? ECU/mapping, MAF, heads etc.
Do think it through......what you have there is a system for getting air into cylinders in a controlled and measured manner. It is made of several components, matched by TVR to give the results they wanted. So they may have similar maximum flows to each other, and if you upgrade all of them you may need to remap your ECU or you will be running lean.gmw9666 said:
Yum yum, mucho wantage right there Out of I interest, what else would you need to make the most out of something like that? ECU/mapping, MAF, heads etc.So changing just one item may not give you the desired result.
You need to make everything to the same standard, so bigger plenum, ported inlet manifold, bigger air filter, bigger inlet tubing? Whatever is the bottleneck will render the other improvements less effective than your debit card would expect
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