Are we missing something? Exhaust Manifold Thread II

[Ragtag]

Gentleman,

 

In no way was I being patronising.

 

I shall bow out of this discussion, I feel it can only end in tears.

 

Tom

 

Not if we all behave like grown ups

[TriumphV8]

Go much over + 40 and you will have head gasket failure,figure that one out.

 

Maybe I have told that earlier:

I actually have +90 over with the VW pistons (77mm)

and +130 over with the MAZDA pistons (78mm).

 

I had gaskets made to my bore by Elmeso Reban in Solingen

http://www.elmeso-reban.de/

 

 

Only disadvantage is that the recess can not be used

because that gets too small with the bigger bores.

 

Possibly this might get problems under race conditions

for street use everything is perfect.

 

Although the head is prepared to meet the bigger bores

and avoids shrouding a little bit I expect with 10% displacement

only 8% power increase due to the VE efficiency suffers.

So the biger engines performs better, but not with better VE

but with simply more displacement.

Edited March 28, 2015 by TriumphV8

[GT6M]

Go much over + 40 and you will have head gasket failure,figure that one out.

Dont tek much figuring, the bore spacings been altered,

so the chambers have been alterd to match, , widened oot

so less valve shrouding..

but as for 40 thou an gaskets gone, maybe on a standard, but this is a diff gasket

at great expence too,

 

M

[Peter Cobbold]

And

If 230 is an engine dyno measurement with no fan, no fan belt, no water pump, no alternator, no car-sized exhaust or silencer there's another 15-20hp liberated to turn the dyno

If so, a true comparison with a road-going 2500cc CP TR6 in standard tune would be nearer 150 vs 210.

And stock is about £15k ? cheaper. A saving of £250 per horsepower.

 

Makes me wonder, what is the most cost-effective engine performance gain? £ per hp.

( Not including measuring in a freezing cold, dry, high pressure atmosphere at sea level )

 

Peter

Edited January 14, 2015 by Peter Cobbold

[Ragtag]

Peter,

 

Going back to your original calculation...............

 

Your source quotes the CFM per BHP as 1.5 to 1.6. It is not easy to find a corroborating source for this and it isn't particularly precise. I found another source that quotes mass air as 1lb to 10 bhp. Converting this back I get 1.3cfm at 15 degrees c

 

This would close the VE gap

 

Then I thought about the fuel. In the real world, an engine that just sucks air won't have any power! We have to allow for the volume of atomised fuel. Doing that opens up the gap again.

 

Doh

[Peter Cobbold]

Chris,

Yes the 1,5 was ballpark figure. Probably based on best bsfc for a typical engine.

Wiki gives best bsfc 273 to 227 g/kwh.

http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption

Dont know best bsfc for TR engine but it will deteriorate at rpm above peak torque, so bsfc at 6000rpm highly liekly to be poor.

The poor bsfc at higher rpm means even more air is needed. The fuel burns fine, but big friction losses soak up a lot of power that never makes it to turn the crank. That works in the direction of needing even bigger VE, actually much bigger, as follows:.

We can get an idea of bsfc deteroirating In the "performance curve" in my blog (below).The horizon of the plot is the torque at wot, the contours bsfc.

BSFC at peak torque (3500rpm ) is 270g/kWh while at 6000rpm it has deteriorated to 350. Air will follow in proportion- a ratio of 350/270 is 30% more air. So we have the probelm that the air is beng used 30% less effectively at high rpm. Which means VE has to rise 30%. 160% 145??.

I now think the 230 is even less plausible. But i need to redo calcs based upon these representative bsfcs. Too tired right now...

 

Yes, fuel evaporation will displace air with its vapour, but it also cools the mixture making it less dense.Will try to find which wins.

 

Peter

 

 

BSFC - I've tried to explain it here:

https://supertrarged.wordpress.com/2013/04/17/tr6se-3/

Edited January 15, 2015 by Peter Cobbold

[Peter Cobbold]

There is a way to cross-check dyno measurements from just three measurements: bhp, Air Fuel Ratio, fuel flow.

The three measurements are made at a fixed rpm at wot.

Then we calculate VE by two different routes:

1. Use fuel flow and bhp to calculate bsfc ( brake spefific fuel consumption ie fuel flow per hp per hour). Knowing the AFR - the air to fuel ratio- we can get brake specific air consumption. And thence VE.

2 Use fuel flow and AFR to get air flow, and hence VE. Here we have no need for a bhp measurement. This is what Andreas did above ( # 51).

If the two calculated VEs agree then we can be confident the bhp data are fine.

But if the VEs differ then the bhp measurement. is suspect. Measuring fuel flow should be precise and difficult to f88k up. AFR can be checked using two, fresh, UEGO sensors.

 

The final check is to look at the bsfc figure from 1 and see if it falls within the bsfc range expected for an si engine ( #86). If it ridiculously low - ie much more hp that the fuel flow would indicate - then again suspect the dyno.

 

"Extraordinary claims need extraordinary evidence"

But its not extraordinarily difficult to get that evidence.

 

Peter

Edited January 15, 2015 by Peter Cobbold

[Mark Shezbo Sherratt]

Must admit I am now really struggling the technical jargon on this thread and all "she said he said" stuff is not really helping?

 

Just going about this logically - there must be a maximum power output a standard TR6 PI - will make (no mods) - regardless of build tolerances and blue printing etc etc whatever anyone says - there is a maximum?

 

Now all the OP was asking was is there any benefit of fitting a different manifold to increase the power? So take the above "perfect engine" scenario...will an extractor manifold increase the power - yes or no.

 

Perhaps that is too simple - then again the last 87 posts have not been very en-lighting?

[Barry911]

Yes, I really started this topic (which was nicked anyway) because frankly being a tight sod, or at least a real-world enthusiast, I was wondering where best to aim my rather small pot of cash: exactly in fact what Peter asked a little further up this page.

 

There clearly is a hypothetical tuning graph where you have power vs pounds. I'm sure there are some early gains that are either free, or very cheap / straightforward, and others at the other end where 1bhp = huge ££'s. I'll be nearer the first than the second, but it would be nice to think there's a sensible sweet spot approaching the middle giving a really lovely, well balanced, torquey and reliable (home buildable, engineering services aside) power plant.

 

Back in my early days of TR Register membership, discussions would have always started from this angle. TBH, for me this is where the fun is.

 

For all that, clearly you're always going to achieve more with the right technical know-how and general understanding of the various thoughts on the subject.

[Peter Cobbold]

Mark,

I think Neil gave Barry the answer above - the stock manifold is fine for Barry's aims.

 

Its no skin of my nose If I cease and desist from posting 'technical jargon'. But it is all bog-standard si engine basics. VE, BSFC, AFR etc etc are all elementary stuff. I know the classic journals and TRA never go anywhere near these topics, for fear of dissuading readership. But if anyone seeks a deeper understanding then I am happy to cater for that minority. Next time I'll start another thread with a "caution jargon" header

 

To answer your question: " .... there must be a maximum power output a standard TR6 PI - will make (no mods) - regardless of build tolerances and blue printing etc etc whatever anyone says - there is a maximum? "

I think Triumph's figure of 150bhp will be right for a standard CP series TR6. Whether that was measured with fan, water-pump alternator fitted, or without, I dont know - and it matters when comparing '150bhp' with rolling road measurements ! But if its not modified in any way how can it work better than factory spec?

 

I agree with Barry, its finding the most cost-effective mods that could usefully be discussed. And for that we need to decide whether its for road use, or rallying or hillclimbing or racing. Many of the power-raising mods seem to me to be racing-derived and so not necessarliy appropriate, or even pleasing, for road driving.

Which is why I follow my own peculiar route.

 

Peter

Edited January 15, 2015 by Peter Cobbold

[Guest ntc]

Peter

Things get out of hand and lose track

Barry

I have sent you pm as I understood exactly what you was asking for

[Mark Shezbo Sherratt]

Peter - I am not adverse to technical jargon - I am a Rolls Royce trained mech eng, however - in the cold light of day - this thread - and I not picking on you - seems to have strayed into the "mine are bigger than yours" category, with regards technicalities?

 

i.e to quote "VEs differ then the bhp measurement. is suspect. Measuring fuel flow should be precise and difficult to f88k up. AFR can be checked using two, fresh, UEGO sensors."

 

All I am saying is that we need - some sense bringing to this - i.e. an extra 20-35 BHP can be achieved via - Routes A - B or C and this will be fine for your road car (as you suggest)

 

I think this thread is done - personally? Start over?

[Tim D.]

Tricky one this..

On one had there is a constituency on the forum that just want a recipe that equates cash to speed and does not nessecary won't to know why. Then there is another constituency that wants to know why. Niether is wrong and in fact the two camps are quite commonly observed in other forums, meetings asnd both are equally relevent (although as we see sometimes they don't live together in harmony:-)

 

One way round this that works is to encourage the more technical discussions on to the "racing" parts of the forum.. Although for the register this is tricky as the different TRs have different needs. The other is to have model specific racing sections? not sure which works best...

 

But whatever there is a need for a list of well evaluated addons to guide the bewildered... The challenge is how to assemble these?

(For the Austin A-series, Vizard had a good crack in his big yellow book... Probably the best example of this out there... Although I agree not faultless)...

 

Cheers

Tim

[Guest ntc]

If Barry replies to pm I will give the answers he requires to achieve his goal and he can feel free to type it on here if it helps.

[Alec Pringle]

To revert to Barry's original point . . . . .

 

Back at the end of the 70s my TR6 CP engine was rebuilt to Prodsports regs of the time, which effectively required standard engines blueprinted - the only deviations from standard being the fitment of +20 Powermax pistons, aligning the ports and the standard manifolds, and some gentle polishing thereof. You don't want to know just how many hours went into working through a stack of new component to find the most equally matched items, balancing to the nth degree etc . . . . . The PI system was also tweaked a little - for top end rather than for touring.

 

My engine man had already built a couple of engines to the same spec, and we had access to an 'industry standard' as opposed to tuning shop engine dyno installation. Engines were all tested to check proper flywheel horse power, as in utilising the engine's own water pump and radiator, all ancillaries attached, standard fan and alternator, and our own modified exhaust system. the latter very much in keeping with the recent observations (now deleted) in terms of twin pipes from the standard manifold and a purpose built transverse box which offered a handful of ponies benefit over standard.

 

Bottom line, a little over 150bhp at the flywheel. That's a good 20bhp increase over production, probably a little more than that.

 

We used the rolling road, chassis dyno installation, for fine tuning, we didn't bother wasting time on calculating mythical 'absolute' figures, irrelevant, it's a comparison tool only for tuning.

 

I'd be pleasantly surprised if anyone ever managed to top a genuine 155bhp from the standard 2.5PI engine utilising the 70s Prodsports specs.

 

The benefits of tubular exhaust manifolds, and we experimented with several, were not great - a handful of horses at best, and some designs offered no benefit over the standard cast manifold, or worse !

 

Different story with a significantly tuned engine however, which is when the tubular manifolds came into their own, with at least double the gain over the standard manifold compared to the increment on the Prodsports spec.

 

Hope that helps Barry ?

 

Cheers

 

Alec

Edited January 15, 2015 by Alec Pringle

[Guest ntc]

That's saved me the bother Alec just to add the gain is lost with transmission worn out.

[GUY BENNETT]

And carrying a ton of spares in the boot!

[Tim D.]

and eating too many pies

[Barry911]

Thank you Alec, Peter and especially Neil for the call.

 

It would seem that the trick is to know which bits to retain (which is a longer list than the retailers would like to see), which bits to massage and then to blueprint and balance as much as possible.

 

For the weary, brow beaten followers of the thread, here is the recipe as sketched by Alec, and fleshed out by Neil over the phone. Neil, hopefully I've understood this right!

 

Background: 1973 US spec engine running twin Strombergs, and a standard Triumph twin down pipe exhaust manifold.

 

Neil's recipe given my budget, the fact I want sensible reliability, decent low down torque, not a rev merchant, and as simple as possible, but something around 140-150 bhp.

 

Have head ported and flowed, then skimmed to give 10:1 compression ratio.

Phosphor bronze guides, stainless valves to reduce friction.

Check distributer and make sure as accurate as possible.

Use SU's on the Stromberg manifold.

Replace damper with new.

Replace single timing chain with duplex.

All new stressed bolts throughout (ARP where poss).

Balance everything to within inch of life, but retain standard weight flywheel because of my driving style.

Cam TBC, although Neil did say a CP Pi one would be nice, but tricky to source. He did have another suggestion, we just need to see if they are still out there.

 

I'm assuming we'd go electric fan, I'm thinking single exhaust system (?), as would look more correct for my 1960's looking Gt, although open to ideas. Also, because I'm looking to lose weight: modern starter, trick battery mid-mounted and out of sight (original area to be changed to a toolbox), alloy engine to bell housing plate, and anything else I can shave. All partly undone I know with my saloon OD gearbox ....

 

Many thanks Gents!

[Barry911]

and eating too many pies

Ahh yes, very good point!

[Alec Pringle]

Hi Barry,

 

head to Peter Burgess, no ifs or buts. Discuss cam with PB too.

 

Dissie to Martin Jay, once you've established cam and head work.

 

Andrew Turner is good for SUs.

 

Why single pipe ? Nothing wrong with twins on a 60s GT. The single is likely to lose grunt, and be more prone to resonance. I'd prefer twins with judicious use of extra u-clamps and an insert in each pipe, at different points, of a heavier gauge piece of pipe . . . . which helps stop the pipes themselves from resonating.

 

The rest is sensible enough, and yes don't lose too much off the flywheel if it's meant to be a Grand Tourer.

 

Cheers

 

Alec

[Barry911]

O.K. Alec, I'm cool with twin pipes if the performance will be alright. I'll let the designer know, and see what he fancies doing.

 

As for flywheel, yes that's an interesting one: Neil suggested leave alone, other than balance. I don't want a snappy chainsaw of an engine, but do understand the benefits of a slightly lighter flywheel.

 

Oh well, if I'm at the point where that's my only worry, we'll have done well!

 

Many thanks again )

[Guest ntc]

Barry

Many try to reinvent the wheel and most fail

[Alec Pringle]

I think we're in agreement re the flywheel - balancing will inevitably lighten it a little, and that's probably sufficient.

 

Grand Tourers should, at least in my book, retain flexibility and be relatively relaxing to drive long distance - they are not out'n'out sports cars.

 

Twin pipes will be fine on a Grand Touring engine, for the same reasons - and easier, I think, to achieve a civilised non-fatiguing exhaust note across the rev band.

 

Cheers

 

Alec

[TRTOM2498PI]

I have a lightweight steel one, balanced at Vibration Free, in Bicester, along with many other engine components. Also have a AP Racing, 3 piece clutch installed. You would not believe it. Drive it on track, enter a Round Britain Reliability Run, 2000 miles in 48hrs, or drive through Europe, no problems at all. Not snappy, nor does it behave like a switch, but also able to absorb the power.

 

 

Cheers.