Moss Blower Kit 2

[Steve P]

Good evening Peter,

Now you have that nice pulley info. Could you now predict the torque using the standard pulley?

 

I've had a bit of a guess and came up with this.

 

Std is where I am now. The new head and cam is a worked head with a fast road cam.

 

 

Cheers

Steve

 

[Peter Cobbold]

Hi Steve,

If you have the horse power curve the torque curve will follow it in precise arithmetic relationship. So its not possible to tuen to get more torque without getting more horse power, or vice versa. The lines appear to be different because:

""......horsepower equals torque (in ft-pounds) times RPM divided by 5250 "

http://www.largiader.com/articles/torque.html

I prefer to read torque curves as they reflect combustion more closely.

 

So there's something odd about the 'new head and cam' curves ( fine dotted lines) -they should intersect at 5250rpm ( torque and hp are always the same number then) . Likewise the supercharged lines dont intersect - very odd - they should.

 

The 'std head and cam' lines are fine, crossing at 5250. Let's work with those.

I can see from the std traces the engine VE starting to fall above 3000-3500rpm. That will also happen supercharged although the tendency for boost to rise will delay and/or lessen the slope a bit. The lines will cross at 5250rpm but at higher values.

Its difficult to calculate at the lower rpm when the VE of the blower falls off. I haven't got VE data for the M62 at lower rpm. The graph in the blog post was for a bigger Eaton blower, more modern. If we had that information the boost at say 1500, 2000 , 2500 crank rpm could be estimated. What you can be sure is that the torque ( or hp) will not be less than the std curve. That's for certain.

My old Wade blower, which is very leaky at low rpm, delivers 6psi at 2800rpm crank, similar to the Eaton I reckon. And 1psi at 1000rpm, 2psi at around 1500. I'd expect the Eaton to be as good as that and probably better. The increase in torque ( and hp) makes for V8-like feel. It just 'pulls'.

 

Peter

 

PS The supercharged versus std power curves look right - around 30- 35hp extra at 3000rpm looks good.

But the supercharged torque curve is not right !

Edited December 17, 2014 by Peter Cobbold

[Steve P]

Hi Peter,

Thanks for the comments. I will post the references I used for the modified and sc curves tomorrow.

 

Cheers Steve

[Tim D.]

As you will have seen am hopefully putting together an sc tr6 over the winter. Would hope to get a rr run in in the spring. Sadly didn't get one in on the PI so we could compare.

Cheers

Tim

[Steve P]

Good afternoon Peter,

The 1st ref was S Coopers dyno results which I had plotted wrong. I've corrected that

The 2nd ref was a plot from a Moss website for a carb cam. I tried to extrapolate the torque and got it really wrong.

 

So below is a revised graph.

To get the SC hp I took the 132 cam max hp (115) added 15hp for a std PI cam (130) then multiplied by 1.25 to get the SC hp.

 

I then used your HP, Torque formula to get the SC torque and came up with the following: I note what you said about the VE after 3000 rpm and I've not factored that in. But if what is below is a realistic assessment of the gains fitting a supercharger to a PI head then I think it is enough justification for me to go the SC route.

 

 

 

P.S. For ref below is the Moss plot for a std carb cam with SC

 

 

Thanks

Steve

[Peter Cobbold]

Hi Steve,

That looks good.

The difference between PI CP-series and CR-series is probably around 10hpaw rather than 15. Triumph used a different calibration that made the later PI look a bit worse than it was.

 

My blog calculation of ca 30% gain suggests you could multiply the CR series (132) by 1.3 and be pretty close to the s/c power. Your 1.25 might be a bit too pessimistic. Although the Moss curves show a gain of around 40% that is with twin Strombergs as a starting point, I guess. So multplying by 1.4 would be too generous with the PI as a starting point. So multiplying by 1.3 is about right, cant get any more precise. The blue power lines have about the right 1.3-fold relationship

The Moss curve indicates that the 40% gain is held down to 1500 rpm. That gives me confidence you will find the blown engine will see good boost even at 1000rpm: it will pull smoothly and feel strong.

cheers

Peter

[Peter Cobbold]

GTT

Unfortunately your opinion doesn't hold water, nor your measurements of air flow though the exhaust valve.

 

Have you stopped to ask why the exhaust valve as Triumph designed it, and in many, many other ic engines, is signifcantly smaller than the inlet? Why- when the exhaust gas is hotter and so more voluminous than the inlet, should the ev be smaller? " because the exhaust stroke begins at higher pressure than the inlet" is the stock answer.

But the main reason is the speed of sound, which dictates the choking velocity of the ev, is a LOT higher for hot gases. Thus:

If the exhaust gas is at 750C then compared with room temperature the choking velocity rises from 343m/sec to about 625m/sec. That means the ev will flow hot exhaust gas twice as fast - a 100% gain - as gas at room temperature.

 

Now, tell us the temperature at which you conducted your ev flow measurements.

 

Peter

 

http://www.engineeringtoolbox.com/air-speed-sound-d_603.html

Edited December 18, 2014 by Peter Cobbold

[Steve P]

I might have confused things slightly.

 

My engine is fitted with a 132hp cam (308778). I had it on a rolling road which indicated that the output was 115hp at the wheels.

I made an assumption that fitting a 150hp cam (307689) I could guestimate a real 15hp increase in hp ie.

 

 

 

At present I have EFI fitted.

 

I then came across this website that suggested that a good EFI installation with a 307689 cam could achieve 136hp

http://www.eficonversions.co.uk/Downloads/TR6%20EFI%20Dyno%20Comparison.pdf

 

Peter, just look at that HP Torque intersect at 5250rpm. Lovely.

 

So I estimated that fitting a 307689 cam with the Moss SC would give gains as detailed in the previous post. Which I think gives a reasonable evaluation of the difference in performance over my current set-up vs stg2 head and fast road cam vs SC on a std PI head with a 307689. Even if the values are not correct one could evaluate the differences in order of magnitude.

[Peter Cobbold]

Hi Steve,

Rolling roads measure the torque and rpm and use that equation to calculate the power, so they always intersect at 5250 !

I am not familiar with the details of those cams, but beware of using one with more overlap than desirable. Might be best to PM RobB

and Marko as they built a hotter blown engine. Too much overlap results in the boosted mixture going straight through the open valves and out the exhaust unburned. It was an old s/c trick to cool the ev, but terrrible for fuel consumption and exhaust pollutants. More lift is good,but its always possible to do that later, even with roller rockers as we dont need to run them up to high revs.

We have to be bit careful though. It might be that 6psi boost is getting close to the detonation zone for the 9.5:1 compression head. Better camming might tip combustion pressures into the knocking zone, purely because more mixture is being compressed compared with the standard engines Moss might have done their testing on. So RobB's engine is interesting. There are tricks to get around 'spark knock' if it happens: use better than 97RON fuel, run really rich under boost, take a bit of lead off the spark ( 'boost retard')., and other more exotic solutions...

 

Peter

 

PS the torque curve on the fast road cam drops rapidly below 2000 rpm. That suggests to me the effect of boost bteeen 1000 and 2000 might be reduced compared with a more standard cam.

Edited December 18, 2014 by Peter Cobbold

[Peter Cobbold]

Steve,

I had another look at A Graham Bell's book for blower cam info. For relatively poor flowing exh valve in relation to inlet valve, and poor flowing exh ports, he advises a cam with exhaust duration 5-15deg longer than the inlet, giving more time for exh gas to exit. Also the cam can be advanced by say 5 deg so that the ev opens earlier when cylinder pressure is higher, so mass gas flow is faster.

Peter

 

Which is pretty much what we read here:

http://www.fbekholden.com/forum/viewtopic.php?f=25&t=18810&p=200077&hilit=exhaust+valve#p200077

Edited December 19, 2014 by Peter Cobbold

[alan atkinson]

You might find this a fun read if you want some real numbers...

 

http://www.6-pack.org/j15/index.php/articles/37

[Steve P]

Good morning Tim,

I forgot to reply to you earlier. My plan was to get the head done and fit a fast road cam in January. Then I started to look into supercharging. Work has got in the way now and I cant see me starting anything till April ish. I'm going to start procuring the hardware early next year. I think it would be interesting for all to see your post conversion RR results.

 

Peter,

I think the "307689" is the part number for the standard 150hp camshaft.

 

Alan,

Very intersting link. Thanks for posting.

 

Thanks

Steve

[Peter Cobbold]

You might find this a fun read if you want some real numbers...

 

http://www.6-pack.org/j15/index.php/articles/37

Thanks Alan.

Supercharged, intercooled and efi is this one:

http://www.6-pack.org/j15/index.php/articles/37/334

 

Peter

Edited December 19, 2014 by Peter Cobbold

[alan atkinson]

Ricks is a home brewed system. The link on that page is out of date - his new site is here.

http://www.pattonmachine.com/tr6/

 

 

He also makes a TBI conversion that fits in the carb bodies - works off an older GM FI setup. It's quite popular over here because it's a fairly easy conversion that isn't especially expensive, but that just seems to work.

http://www.pattonmachine.com/TBI-Components.htm

[Peter Cobbold]

Ricks is a home brewed system. The link on that page is out of date - his new site is here.

http://www.pattonmachine.com/tr6/

 

 

He also makes a TBI conversion that fits in the carb bodies - works off an older GM FI setup. It's quite popular over here because it's a fairly easy conversion that isn't especially expensive, but that just seems to work.

http://www.pattonmachine.com/TBI-Components.htm

Thanks Alan,

It gives impressive power, at 5000rpm: 170 at wheels, maybe 200 at flywheel, and another 10 to drive the blower. So 210 bhp.

I'm puzzled why he didnt put a big butterfly before the blower, it would save having to switch the blower on and that clutched pulley.

Looks like he's very pleased with the outcome !

That blower cam is worth investigating even for more modest installations.

Peter

Edited December 19, 2014 by Peter Cobbold

[PaulAA]

Almost exactly what I said.

200 yankee horsepower = approx 150DIN REAL, 160 if you are lucky.

 

You can't beat the laws of science, especially if you don't actually ever measure anything.

 

 

 

As an attentive and interested reader of the Moss and camshaft threads, I have to say that your vitriolic interruptions have become a little... tedious. Am I correct in thinking that you are trying to sell an exhaust manifold?

 

Unless your intention is solely to distrupt, I would respectfully suggest it is time to put your c**k on the block and state clearly, without hyperbole, repetition or accusation, what your considered engineering approach would be. I, for one, would be most interested to discover what you actually have to say.

 

Of course, you might have stated it already, but I get rather bored by the second sentence of your posts and move on.

 

Keen to discover, etc.

Edited December 19, 2014 by PaulAA

[PaulAA]

... and?

[PaulAA]

Okay, you did lots and lots of testing. What is your conclusion and what is your engineering approach?

 

I don't claim to speak for everybody, but, personally, I rather conclude that you want to bait and don't actually have anything of substance to add to the debate.

 

Of course, I'm happy to be proven wrong.

 

Over to you.

[GT6M]

Gareth, in your findings, is it possible for a 2.6 to acheive 190 lb/ft at 2.7 rpms

if the comp ratio was 10.8.1 on injection {EFI } with a 132 cam with 1/65 rockers.

 

Or 180 on 2 x 1 3/4 SUs

 

it would certainly be well over 220-240 lb ft on a supercharged engine

and its SC the OE post was about.

 

I think most of the power charts were for the US spec engine with v v low comp ratios

hence they were still only getting some where near a ..decent tuned.. N/A engine over here.

 

comments, just curious.

 

M

[Peter Cobbold]

 

 

 

The TR6 engine CANNOT exceed more than 60cfm of flow in that time, quite simply meaning A+B = you cannot get more than 25bhp per cylinder however hard you try.

 

25bhp per cylinder = 150bhp.

 

 

 

 

 

 

I'd value your input as to how this was acheived: 210hp at the crank, 200 at flywheel after subtracting blower take.

At 5000rpm.

http://www.6-pack.org/spaw/dyno/patton.jpg

And a beautifully flat torque curve from low rpm.

I can see the intercooler raising the density ratio, hence the extra power above the Moss approach.

But, taking on board your earlier comments about ev restrictions, how can the exhaust valves cope with that all that extra gas in the Patten engine? Doesn't the port-stem area become the limiting obstruction, above a certain ev lift? All I can think is the exhaust stroke is consuming a lot more power to expel the gas than a n/a engine, but that cost is hidden from the dyno data.

 

I agree with you that supercharging is all about lots of torque from low rpm. Diesel-like is right.. and it's like having two extra cylinders bolted-on.

And point it up a hill...up it goes.

 

I take your point about heat, it very well known, its fundamental. But not all of us want the complexity of intercoolers, by-passes and efi, or the expense of Lysolms.

Heat soak would be an issue if high boost were run continuously. But for a road car it isn't, with the possible exception of alpine climbs.

 

 

Peter

[Peter Cobbold]

As this is a post about blowers I'm writing this to explain why advancing a cam 5-10 degrees helps a blown engine. It is a well known trick to improve power from a stock cam.

Whan an ev first opens it does so in a normally aspirated engine before BDC when there is maybe maybe 2 bar pressure at the end of the expansion (aka power) stroke. In a blown engine expansion continues much longer into the power stroke - hence the torque gain - and cylinder pressure at exhaust valve opening (evo ) will be higher. Now, if the cam is advanced a few degrees then that pressure can be several-fold greater at evo than the n/a engine. This pressure is very important:

That period immediately following evo is when the majority of the gas escapes the cylinder. In fact there is a huge surge of gas as the crank is crossing BDC, followed by a slowing to a minimum flow then a second rise as the piston pushes gas up the bore. But the majority of the exhaust flow happens because of the end-expansion pressure driving it out.

We can see this happening in the left side of this plot, the red line: ( ignore the right side)

http://t0.gstatic.com/images?q=tbn:ANd9GcRIvQXGrAh8w5n8quDFI5BXPIoy0QqLL5TDbqwIfeBsH5Zy4JZ-Rw

Eyeballing the are under the curve tell us how much gas mass has flowed since evo, and the majority of the area happens as the valve is opening ( dotted line). Indeed most of the flow occurs when the piston is still moving downwards !!!

Take home: Cylinder pressure before and at bdc is very important for most of the exhaust gas flow. The quantity 'pushed out by the rising piston' is small in comparison. Advancing a stock cam so that evo is early in a blown engine enhances this process.

 

Peter

 

The very start of the gas flow as the valve cracks open is at the speed of sound - those bursts of sonic shockwaves make the exhaust note

Edited December 19, 2014 by Peter Cobbold

[littlejim]

Now some valve shapes for you:-

We bought from everyone, put them in a nice photo studio, photographed them and tested every single one on the flow bench.

 

 

You know how much such work costs commercially?

100s and 100s of pounds, just to get close to a valid result.

 

If you want to carry on being bored, your opinion isn't shared by everyone, which is why I tend to be a tad direct when I paid for all this stuff.

The late Alan Staniforth had a bit of a muck around with different valve shapes and settled on the "penny on a stick" shape.

Suspect, but don't know, that the lower mass rather than the shape, came into play at revs.

[Peter Cobbold]

Gareth,

Oh silly me. I thought Alan Allard, A Graham Bell and many other published supercharging gurus were right about advancing the cam. I stand corrected.

And what an idiot I am to believe what I read (section 6.5 covers mass gas flow vs evo) in Heywood's textbook:

http://www.amazon.co.uk/INTERNAL-COMBUSTION-ENGINE-FUN-Intl/dp/0071004998/ref=sr_1_sc_1?ie=UTF8&qid=1419028880&sr=8-1-spell&keywords=Jhn+b+Heywood#reader_0071004998

After all Heywood is merely a Prof at MIT:

http://meche.mit.edu/people/?id=43

and directs a laboratory:

http://web.mit.edu/sloan-auto-lab/

Just shows, we cant believe everything we read in books.

 

Peter

 

I give up.

Edited December 19, 2014 by Peter Cobbold

[Alec Pringle]

Apart from which, it ain't just what he writes, it's the way that he writes it . . . . that's what gets the all too predictable results . . . .

 

Cheers

 

Alec

[alan atkinson]

The TR6 engine CANNOT exceed more than 60cfm of flow in that time, quite simply meaning A+B = you cannot get more than 25bhp per cylinder however hard you try.

 

25bhp per cylinder = 150bhp.

 

QED.

 

 

I wish I was as smart as you.

I'd be wondering how my old 6 engine - fitted with a supercharger cam (custom grind from a guy in the USA) running at a measured 8.5:1 CR - managed to engine dyno at 163hp on triple ZS.

 

It's the same one that hit 125hp rw on a mustang dyno, which tend to not overestimate too much. I have both dyno sheets.

The engine builder is quite reputable - mine was one of the cheaper ones he'd ever touched.

Perhaps I should sue him because clearly he lied...

 

Just saying.

 

Of course the 15k quote for the "proper" intercooler supercharger setup was the final straw.

Why aim for 300bhp when you can buy 400+ for $5400?

 

Edited December 20, 2014 by alan atkinson