Exhaust power

[pfenlon]

My 69 USA gasper engine has been rebuilt and I fitted it today.

 

The exhaust has a single outlet and I note that the later versions have a double exit hole and twin pipes exiting the head.

 

Is it worth upgrading for street driving?

 

Running a 2500s Cam TR6 PI compression Cylinder head, 30+ rebore standard crank, and Stromberg carbs.

 

Don't want PI, its never been bullet proof, but is more powerful when it works properly I do know having had a couple.

 

But it doesn't work properly all the time, it may have done in yesteryear but not today.

Edited July 5, 2017 by pfenlon

[TriumphV8]

I always do the swap to double exhaust when tuning.

Honestly I do not know the difference in power.

 

I am very interested in a back to back test made by

a serious, reliable person on all the headers we are

talking about from time to time.

 

I would do the swap with a complete PI exhaust system, maybe

the Phoenix I have. Looks and sounds nice and is stainless.

 

With a 270 or 280 degree sports cam you can get easily 125 BHP

and with some effort up to 150 BHP, all with twin carbs.

So you are on the PI level without the problems you envisage

although they can be overcome in these days.

 

If you do not like PI you may take a look at EFI I use for more

than 10 years without trouble.

 

Another idea is the three carb system, easy to install and with

the power gain in the middle between twin carbs and EFI.

 

..... and not to forget the blower Peter will recommend to get

a fantastic torque and much power out of the box.......

[TR NIALL]

Think it worth changing to the Twin as the Flow is know to be there,should be plenty knocking around due to Banana Upgrades.

[Nigel Triumph]

If you're considering switching to the twin outlet silencer, Phoenix make a big bore stainless version. It looks standard except for bigger polished tailpipes, fits to the standard twin pipes and should be slightly less restrictive than the original. Or go the whole hog as Andreas suggests and fit a 6-3-1 manifold.

 

Nigel

[pfenlon]

Thanks lads, Bitz are sorting me one out.

 

Andreas, I did have an EFI TR6 a vauxhall system designed by Mike on the Wirral, it ran well, but I didn't notice a huge power difference if at all, compared with PI.

[TriumphV8]

That is not the aim of the EFI. If PI is set perfect for power the EFI can not do better.

My system uses the original PI manifold, so all is the same as PI.

 

The advantage is that it uses lower fuel pressure what makes the whole pump

arrangement easier and it has a sweat setup utility with laptop to find the best

values without the need to use a rolling road eqipment.

 

So with EFI you will find setup easier, may extend to ignition timing and watch and

record the data during drive if you like. You can go lean at part throttle, rich at full throttle

and can give part throttle ignition advance. All that will bring fuel consumption down

without sacrificing driveability.

 

It is a lot of work in the beginning with some parts to be manufactured but

it pays back when setting and controlling fuel and ignition.

 

If a PI runs quite well I would not recommend to swap. I had a USA car

with a cut off evaporation filter system and the engine run badly. I had

my experience with MegaSquirt and so I sorted all out with EFI.......

[YankeeTR5]

Well, its a bit old at this point, but Kas Kastner's TR250/TR6 Competition Preparation Manual for the factory backed North American racing team did do a test of the single vs dual pipe system and makes the claim, strongly, that the single pipe performed better than the dual system. Slightly larger diameter pipe than stock, but still he pushed for the single pipe. He was also pretty complimentary about the standard exhaust manifold from the factory.

[john.r.davies]

Always remember Pouiseuilles Law (yes, really!)

Flow depends on the fourth power (X x X x X x X) of the radius. Double the radius and the flow goes up SIXTEEN tines. So a single larger tube need not be much wider than two smaller tubes to flow better.

[Peter Cobbold]

Always remember Pouiseuilles Law (yes, really!)

Flow depends on the fourth power (X x X x X x X) of the radius. Double the radius and the flow goes up SIXTEEN tines. So a single larger tube need not be much wider than two smaller tubes to flow better.

Poiseuille only applies to laminar flow of viscous fluids like heavy oil, or extremely slow-moving gases. Exhaust gas flow will be highly turbulent. The Moody diagram is a way into calculating the head loss for different velocities and pipe diameters. I've never used it ....but feel free:

https://en.wikipedia.org/wiki/Moody_chart

The pressure drop is proportional to gas velocity squared.

Peter

Edited July 12, 2017 by Peter Cobbold

[Hamish]

There is a reason this is posted in the

"TR Technical Chat" section ????

This is blinding me with science

Or have you just baffled me with male bovine faeces ?

[Peter Cobbold]

There is a reason this is posted in the

"TR Technical Chat" section

This is blinding me with science

Or have you just baffled me with male bovine faeces ?

Like John I 'did' Poiseuille in school physics. But it applies only to laminar flows, like a thick oil flowing steadily along a straight pipe.

Moody is pukka fluid mechanics that applies to turbulent flows of fast moving liquids or gases. But it will give only a rough idea of back pressure as the exhaust flow is not steady. Probably the true back pressures have to be found by measurement.

 

Fluid mechanics is fundamental to the design and operation of the ic engine. For instance, look at the diameters of the inlet and exhaust valves in any TR. Why is the ev always smaller? There is an explanation in fm of that. Answers on a postcard......

 

 

Peter

[HSM]

Hello Peter

Fluid mechanics applied to heat engines is a very interesting subject,

the relationship between valve, port & inlet size etc. I can sense a

seminar subject for next year perhaps ?

 

Regards Harvey

[Peter Cobbold]

Hello Peter

Fluid mechanics applied to heat engines is a very interesting subject,

the relationship between valve, port & inlet size etc. I can sense a

seminar subject for next year perhaps ?

 

Regards Harvey

Hi Harvey,

Another seminar ?? -not if I have to learn semaphore to be 'heard'.

But I'd be very happy to listen to your expertise !

Best, Peter

[Tom Fremont]

Hi Pete,

 

I don't think you're going to see a noticeable difference between factory single and twin exhausts, based on my experience with Webers where I've had both factory manifolds.

 

I do, however, think you will see quite a bit of difference if you fit 3x40DCOE Webers regardless of which manifold you use ! You're practically there now, with the easy bit remaining ( engine mods on board already ).

 

Cheers,

Tom

[Ade-TR4]

How about a "webinar" Peter?

 

Ade

[Peter Cobbold]

How about a "webinar" Peter?

 

Ade

Ade,

I've no experience of doing that- and suspect it can look rubbish..... needs rehearsing. I didn't have TV until age 18 ! So for me the written word rules. But a bald power point is not ideal -maybe this winter I'll add text to support each slide.

Peter

[john.r.davies]

Thank you, Peter!

Such informative correction is always welcome.

 

Yes,a square law for turbulent fluids (inc gases), so a tube twice as big will only flow four times more. Still greater than two tube of the same size!

 

John

PS actually I did Pouiseuille for my graduate medical qualification but physics applies everywhere!

Edited July 14, 2017 by john.r.davies