Trumpet Base Blending,

Post by **Coops** » Sat Jan 10, 2015 6:38 pm

what im using at the moment yes and think they are about 36mm standard???

Eliot · Post by **Eliot** » Sun Jan 11, 2015 10:30 am

Standard trumpets and base is 38mm. If you manifold is 42mm, you are not getting the best out of it imo.

Post by **Coops** » Sun Jan 11, 2015 1:07 pm

looks like im needing a ported intake too,
more money then

stevieturbo · Post by **stevieturbo** » Sun Jan 11, 2015 1:27 pm

There's a difference between needing, and wanting.

I wouldnt go nuts spending lots of money with this, as I really dont feel you'll gain much.

Let the blower do the work for you, it's already there so effectively free.

And as it is a blower and pumping air all the time, it will make any benefits from the manifold much smaller than they might be with n/a

Eliot · Post by **Eliot** » Sun Jan 11, 2015 10:13 pm

Coops wrote:looks like im needing a ported intake too,
more money then

ported intake? I thought you said the inlet manifold is 42mm? What are you referring to with "ported intake"

v8250 · Post by **v8250** » Sun Jan 11, 2015 11:22 pm

Tony, if you're needing any porting/opening out, have you spoken with James Goldstraw at Grace Engine Developements in Newbury? They do good work and are correctly priced.

Post by **Coops** » Mon Jan 12, 2015 12:26 am

i may of got things crossed Eliot.

are you saying using the 38mm trumpet base on my 42mm manifold is not getting the best out of it? which is what i know hence why looking at the trumpet base opening out and ditch the trumpets,

or that standard its only 38mm and mines only 42mm (which is what i thought you meant) is why its no good,

stevieturbo · Post by **stevieturbo** » Mon Jan 12, 2015 12:29 am

If you can get some porting done at a sensible price, go ahead, but really dont spend a fortune on this.

A cam swap would likely give better results per ££ outlay.

It's not like n/a or even turbo where off boost you're reliant on atmospheric pressure to a certain point. With the centri it is shifting air all the time, even at lower loads and throttle openings, and even when it appears there is no boost. It is still helping move air.

dbv8 · Post by **dbv8** » Mon Jan 12, 2015 9:26 am

I ported my own inlet manifold to about 43mm first using a plumbers drill bit then a few hours with carbide bits, files, flapper wheels, emery etc
Similar withe the trumpet base. Voids were filled with chemical metal. Not the prettiest of work but its worked well for me. I was concerned about fuel gathering in the voids from the nitrous injectors.
My NA is 329bhp on a 4.6 so seems to work well.

mgbv8 · Post by **mgbv8** » Tue Jan 13, 2015 9:26 pm

If you are using boost and nitrous I cant see that the blending thing will make a huge difference ?

Pel

dbv8 · Post by **dbv8** » Wed Jan 14, 2015 8:23 am

I agree that in a FI application the charger will do the work and overcome most usual NA restrictions.
NA tuning is also important to me. Its a known fact that the old 38mm inlet and trumpets strangle the higher capacity and tuned RV8s. Its common practice in the TVR community to upgrade to 45mm. Most prefer flaired trumpets and get excellent torque with free high rev breathing also.
I opted to do away with the trumpets and blend the base due to my nitrous application with fuel entering the plenum.
I am sure there are also benefits to be had in FI applications also but it may be negligable when all you need to do is up the boost marginally to overcome any restrictions.

stevieturbo · Post by **stevieturbo** » Wed Jan 14, 2015 3:40 pm

It's not so much about the boost overcoming any restriction, but because there is boost there, the restriction for any given power level just may not be there in the first place.

It's the same with turbochargers. You might think that weedy small manifold and turbine housing will strangle the engine. Far from it in reality.

But as said, by all means do it on a budget, but dont go crazy spending a fortune. IMO it will not bee good value for money in terms of end performance.

A cam swap would likely be cheaper and offer more potential

DaviesDJ · Post by **DaviesDJ** » Sun Jan 18, 2015 10:21 pm

I think a cam swap would lead to a few issues. Overlap plays a part here as I think coops is approaching 11:1 CR.

stevieturbo · Post by **stevieturbo** » Sun Jan 18, 2015 10:24 pm

I dont know what cam he has, and nobody suggest more overlap. But then we dont know how much overlap he has to suggest whether more or less might be appropriate.

There are dozens of profile options or a custom grind option, but there are many many variables.

dbv8 · Post by **dbv8** » Mon Jan 19, 2015 9:22 am

For cam advice i would recommend a chat with Rob Robertson. Give the full spec and requirements and he will choose or spec you a custom grind.
Lots of modified TVR owners happy with his work.
Top guy.