Big Valve Trx Dyno Results

[sanddune51]

I rode the bike over to the same dyno where I tested it as standard.

Specification now

868cc (+1mm Yamaha Trx pistons)
41mm Keihin FCR carbs
Home ported, skimmed head with 1mm oversized valves
11.8 : 1 compression ratio
Kent cams
Art cans (with Db killers fitted)

Specification when previously dyno tested

All standard except Art cans (with Db killers fitted)

2 runs were made on the rollers with no adjustments at all made to the bike to optimise it in any way.





The above is power (bhp) before and after modification




The above is torque in pounds-feet before and after modification.

To say I'm well chuffed would be an understatement. I rattled on and on about trying to get lots of midrange at the expense of big peak power at high revs during my build and I reckon I've achieved my goal.

Peak torque is raised 15.5% from 56.05 to 64.76 lb-ft but now has more than the previous 56 lb-ft spanning 3900 revs. I'm pleased also to have greater than 60 lb-ft of torque spanning 2600 revs, right where I want it (4900 RPM -7200RPM).

Peak power is lifted 23.5% from 72.78 to 90.0 bhp and the motor now has more than 74 bhp for greater than 2500revs.

It's an absolute delight on the road, even in heavy traffic, and will even pull cleanly right down to 2500rpm in third (20mph).

Hope this offers encouragement to all the guys with big valves. An professional tuner ought to produce comparable results and more than likely much better.



Mark.

[coxylaad]

good work. A big increase in output there.

I wonder how much of that is down to the valves and how much is down to the carb swap?

[Killerwhale]

...and there´s the infamous dip
You had a lovely 12 degrees first run, should give some more at that temp me thinks...

Gonna run down with the bike and valves in late sep...early oct and then we have a swedish result as well.
Just gonna do the valves and a skim.....12-13:1 something....

[sanddune51]

Thanks.

I tried just the carbs alone for a trackday at Brands and there was a big improvement, now with the head modded, the improvement feels huge. Probably half of the improvement attributable to carbs and half to the other mods (head flow,squish and deck clearance, and cams)

The temp difference between the runs is compensated for by the dyno itself.

Although the torque dips a little on the graph, the power curve keeps on rising. This is due to the rate of increase of engine speed (acceleration ) outpacing the reduction in torque.
Sometimes a big hole in the torque curve causes a dip in power. This is a far more serious situation and is due to the fall in torque being greater than the rate of increase of engine speed.

Good luck with engine build in the Autumn KW .


Mark.

[Killerwhale]

Good luck with engine build in the Autumn KW .


Mark.

Thanks! I will take a look at some other bikes he dynoed, thinking mostly of monster 900...for a fair comparison.
Then it´s easy to see how moderate/happy go lucky the dyno is...

[cobbadiggabuddyblooo]

Could this drop as we all seem to come across be attributed to the accelerator pump???... This i feel may become more apparent when Rod does his mods to my exhaust to utilise the O2 sensors to run on the bike. With a good range of 30 or so needles and tinkering with mainjets I'm sure this can be ironed out.


There are also options with a 4 piece set that changes the discharge rate. This ulters how the diaphram works on the Acc pump. this controls the stroke which ultimately determines the amount of fuel discharged through accaleration..

You can also adjust the flow rate capacity and increase/decrease that by the diaphram cover.




I have a comprehensive manual on the fcr and tuning methods to iron out problems with modifications air/fuel mix, jets and acc pump operation including a multi squirt jet mod..

[Rod.s]

Could this drop as we all seem to come across be attributed to the accelerator pump???... This i feel may become more apparent when Rod does his mods to my exhaust to utilise the O2 sensors to run on the bike. With a good range of 30 or so needles and tinkering with mainjets I'm sure this can be ironed out.


There are also options with a 4 piece set that changes the discharge rate. This ulters how the diaphram works on the Acc pump. this controls the stroke which ultimately determines the amount of fuel discharged through accaleration..

You can also adjust the flow rate capacity and increase/decrease that by the diaphram cover.




I have a comprehensive manual on the fcr and tuning methods to iron out problems with modifications air/fuel mix, jets and acc pump operation including a multi squirt jet mod..

Mate talk to you later, as there is an easier and cheaper way to achieve all this, it's far less cumbersome and infinitely adjustable! The only two mods need on these is, 1. adjust the accelerator pump time 2. tune the squirt volume...

Remember.....Sheds are for beer, not for testing jetting

Rod

[trixynut]

Not bad results there matey ........... and I don't want to put a downer on this, but.....

With that spec, tbh I would have hoped for a little more BHP.

Yep, we all know different dynos read differently, but I put just some FCR41s and pod filters on a bog standard motor just with a bigger bore 2 into 2 renegade system and got 89.

Phuk and Honk and steve speed (and maybe others) had similar specs to yours (cams, head work, overbore, fcr's, BUT also akra headers and free flowing cans) and got between 98 and 101 iirc.....?

Maybe its time to look at your headers and cans....???

Still, good work so far.

[sanddune51]

Thanks Dave, I'm really pleased.

As we all know theres dynos and theres dynos . I'm happy that the curves I've posted at the top of the thread are are accurate and representative of the shape of both the torque and power curves. These curves are plotted in large scale against engine speed.
They show quantitatively where torque and power have improved. Yes, I think the std headers my be negating some of the "breathing" improvements I've achieved in the head so will need to attend to that.

Would my bike suddenly become massively better by putting it on dyno that measures its output at 100 hp in it's current state? Of course not. I've dyno tested a lot of my race bikes over the years, being careful to use the same dyno before and after. Without that simple control any dyno graph comparison would be made useless.

Out of interest I have searched and found the thread you may be referring to
viewtopic.php?f=5&t=664&hilit=CV+vs+FCR

The graph seems to be "through the gears" but doesn't state which gears .

The torque curve would make for an interesting analysis of how well the engine has been modified, but the torque scale on the right hand side has been neatly cropped off. I think it may have been kg-m but am not certain of this. If the torque is measured other than imperial (lb-ft) or S.I. units (Nm) might the horsepower units be non std too . There are very many units of horsepower.

The baseline axis is would be really useful if engine speed (r.p.m.) was used but I can't tell what is going on.

What I am trying to show is that with so many variables, meaningful comparisons are pointless.

I have chatted with Phil "misterdimwiddy", who has kindly allowed me to make a direct comparison between my bike after modification and his track bike on the same dyno.

Phils spec at that time was:
878cc
JE pistons
FCR 41's with Ramair filters over bell mouths
Akra 2-1 with Devil can
Standard head and cams

So, essentially mine has the head and cams and Phils has a little extra capacity and the Akra 2-1 with Devil can.
Phils curve is red and mine is blue.
http://i959.photobucket.com/albums/ae79 ... 2e0268.jpg

I'm pretty sure both Phil and I have more to coax ou of our engines but doubt that 100bhp is attainable on this particular dyno .


Mark.


edited to correct Phils spec. Hope that's correct mate.

[misterdimwiddy]

Mark

Spec for my motor was correct.

Nice to see how close our power traces are when over laid.

My thinking over the weekend was along these lines. My head and valves are bog standard (it's quite a high ileage gead as mine smokes on down changes) and yet I have the Akra/Devil system. Yours with head skim, porting and over size valves is almost identical in power output.

I wonder therefore if the head mods are pretty much equivalent to my pipe/headers and with these combined the output would be bumped up quite a bit towards the 100rwhp?

Could meet you for another dyno run s'time and pop my system on your motor to quantify the gains to be had from the exhaust.

Whatever the numbers, the joy of having a tuned TRX is huge.

I received the inlet valve today and will take some pics tmrw at work. Was it a middle or outer one? Looks to be in a bad way even with my eyes!

Phil

[misterdimwiddy]

That was supposed to read 'high mileage head'...............stupid fingers.

[Yoozy]

I'm chuckling here boys, just been on the Tuono up Nesbitville in some shitty weather and slutchy roads, and to be honest the T was too much at times, and I was thinking I wish I was on the Rex in a lot of places

Crazy mofo's

[cobbadiggabuddyblooo]

I can see exactly where Mark is coming from. It's great to see a single base/reference point being the same dyno and comparissions from there. The shop where I had my dyno's done has now closed down so I have to start from a new common point with this motor rebuild and base everything around that once again.

[sanddune51]

Phil

It would be great to do a dyno run with your Akra on my bike. I have a hunch that my (hopefully) high flow head would benefit from a free flow exhaust more than a std head would. It would be really good to check that this is actually the case, thanks for the offer .
Agreed the fun that derives from a tuned Trx can't be overstated,so agile and torquey and real world fast.

Yes the valve I sent you was indeed a centre one. You can see how a valve in this state would close up the tappet clearance somewhat .

Cobba,sorry you have lost your local dyno house. Hope you don't have to travel too far to find a good one when your motor is fully rebuilt. Roll on mid December. I might have even sorted myself some sort of pipe by then .


Mark.

[Silver]

Be nice to get out on track with you two and my std nail and see how far back i am. Cadwell anyone? he he!
Dave