Turbo

Is there any way of making a turbo to work on low rpm?

 

Not unless the engine turning it is a diesel, no, not really.

You need a certain amount of exhaust gases to spin a turbo properly.

 

Thanks
1)
what would be a minimum rpm if we take an example of
the Suzuki Bandit which is often used as a basis
AND
2)
What about mechanical chargers, belt driven?
Has anyone ever used it on a motorcycle

 

God knows. What size of Bandit? 400, 600, 1200? You'd need to know the
size of the turbo, the voume of gas flowing, and a myriad other things.

You mean a supercharger. Yes, superchargers have been very successfully
used on motorcycles, although (AFAIK) no manufacturer has ever made a
production road version. I think DKW or someone did a supercharged
two-stroke racer in the mid-to-late 1930s.

 

1200 and the smallest possible turbo
but as I guess from the above answer, your mileage varies...
eg. it depends on so many other things, too
Be all free to give any possible info

Hmmm...it might be interesting
but I have been told by the commercial turbo-builders in Finland
that a supercharger would be much more expensive

Feel free to give more info on the subject

 

Well, in theory a turbo is simpler as it needs no mechanical drive from
the engine. However, a supercharger delivers extra power more or less
everywhere, whereas a turbo generally only starts working once the
exhaust gases have spun the turbine up to a certain speed.

There are plenty of turbo kits around, whereas supercharger kits are
*very* rare, so I guess what you've been told is true.

 

Haa!
There is a delay in the turbo (unless it's quite small)

:-(
Then I think it might be better to rise the compression ratio
(and use Euro 98E eg. "super" gasoline)
This time I'm thinking of the Suzuki GSX-1400

What if the timing is slightly advanced?
I still want a have a little bit More torque (and perhaps power)
on close to the idling rpm
OR
should I consider the new Kawa,
which has 10kpm or 98Nm of torque at 2000 rpm
and can go on from a stop "on almost any gear"
according to the marketing text

 

1200 and the smallest possible turbo


Dale Walker is reputedly the expert on Bandit performance. Check out
www.holeshot.com.

Good luck.

 

The GSX1400 is in a very 'soft' state of tune, and there are many kits
out there to increase the power.

I'd start with a fuel injection re-chip, and a different exhaust.

 

Select a turbo with a smaller internal volume in the scroll case. IOW
the impeller is closer to the case, so the impeller doesn't have to
compress the air as much before pushing it on to the intake tract.

The air has to move on into the engine sooner.

Also, shorten the intake tract as much as possible, by mounting the
turbo on a manifold where the carbs would usually go, even though this
means a long ugly exhaust middle pipe snaking up there.

A tuned header is defeated by the turbo anyway.

I used to have a great book on turbocharging and nitrous oxide
injection by a guy named Innes, as I recall. I may still have it packed
away. It was one of the series of hotrodding paperbacks by HP Books.

Innes talked about "efficiency islands" and showed graphs of how turbos
with smaller clearance volumes in the cases "spooled up" quicker than
turbos with larger volumes in the impeler cases.

 

Select a turbo with a smaller internal volume in the scroll case. IOW
the impeller is closer to the case, so the impeller doesn't have to
compress the air as much before pushing it on to the intake tract.

The air has to move on into the engine sooner.

Also, shorten the intake tract as much as possible, by mounting the
turbo on a manifold where the carbs would usually go, even though this
means a long ugly exhaust middle pipe snaking up there.

A tuned header is defeated by the turbo anyway.

I used to have a great book on turbocharging and nitrous oxide
injection by a guy named Innes, as I recall. I may still have it packed
away. It was one of the series of hotrodding paperbacks by HP Books.

Innes talked about "efficiency islands" and showed graphs of how turbos
with smaller clearance volumes in the cases "spooled up" quicker than
turbos with larger volumes in the impeler cases.

 

a low rpm turbo? I suppose you could make one but I am afraid that the size
would be rather large. If you want something to move air at low rpm you need
to make it really big.

pierce

 

My impression is the guy wants more "grunt" at low _engine_ rpm. The
previous suggestion of a smaller-vaned turbo combined with a greater
restriction in the exhaust pipe would do it: less volume in the vanes
means lower volume of exhaust gas necessary to spin it up to speed. More
restriction means higher pressure differential between the high- and
low-pressure sides of the turbo, and it's the pressure differential
that's doing the work.

However, it's not going to provide as much boost as a larger turbo.
Two-stage turbochargers get around this problem by having both a small
turbo (for quicker response right off idle) and a larger turbo (for high
volumes of air at WOT). That's probably more than the OP wants to mess
with, though.

This is, of course, where the supercharger is superior: it provides
boost from idle upwards, without lag. As the OP has found, they are
somewhat more expensive than turbochargers for these applications.
There's also other means of increasing torque at low engine rpm, without
moving to forced induction (e.g. higher compression pistons and/or
head), but gains are more modest.

--
Later,
John



'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.

 

EXACTLY, John-John! <top-posting>

No, no 2-turbo, the small one is all I need,
I don't want much more horsepower at the high end

There is a spacer or some kind of seal between the upper part of the
cylinder block
and the lower part where most of the engine is
Using 1mm thinner seal would give more compression out of the GSX-1400
This can be reversed and it's cheaper than new parts
<bottom-posting>
to please you all ;-)

 

Day-ummm! You done *exposed* yerrself in public! You just made a idjit
outta yerrself in front of the whole forum, Brother-Peter! "There is a
spacer or some kind of seal..." ;-)

Well, maybe Nomen Nescio wouldn't understand that you're calling the
*head gasket* a "spacer or some kind of seal". ;-)

But, no matter. We all have to learn some way.

The basic procedures of hotrodding are to increase engine displacement
(if the rules allow), supercharge or turbocharge (if allowed), use
oxygen-bearing fuels, or if the engine builder is stuck with engine
size limits, he improves upon the cams, carburetors, and compression
ratio, in order to make the engine operate at a higher RPM and gain the
extra horsepower that way.

Cams. Carburetors. Compression. They *all* work together.

With higher compression, you can use a camshaft with longer duration.
Many newbies forget that the opposite is true. With a wilder camshaft,
you NEED higher compression to maintain low RPM torque at a level that
will get the car off the line without using a lot of RPM, which would
make the car hard to drive on the street.

And then there is camshaft degreeing. Have you ever degreed a camshaft?
You can get the engine to "dig" better if you advance the intake valve
closing point in terms of "lobe center" degrees, or you can make the
engine produce more top end power by retarding the intake valve closing
point.

You can simulate a camshaft of a different duration by degreeing it. I
didn't understand why hotrodders were dicking around with dial
indicators and degree wheels after building their engines. For years I
thought that the cam timing marks were good enough to "get 'er done".
Then a hotrodder convinced me to degree the cams on my GS-1100,
advancing the timing about 2.5 degrees on both intake and exhaust cams.

Oh. My. Gawd. It works. The engine digs so much better. I get into 5th
gear by 60 mph, short shifting. The motorbike is much more fun to ride
in the lower RPM ranges, I don't need to ride at 120 mph to feel the
torque. And it still revs up to 9K, which was the stock redline anyway.

Would-be hotrodders always got the impression that there was some
magical increase in power to be gained from "milling the head" and
doing nothing else.

And others figured that there was some horsepower advantage from the
thinner stamped metal head gaskets with formed ridges instead of a
metal/asbestos sandwich. They figured that the engineers in Detroit
were just hotrodders at heart, which wasn't untrue.

Back when gasoline was very low octane, 4:1 or 5:1 compression was all
that could be used. When reformed and leaded gasoline became available
it was possible to use 7:1 or 8:1 compression and improve the
efficiency of the engine. If you can raise the compression ratio from
5:1 to 10:1 and burn the mixture at a higher temperature, you get
almost 13% increase in air standard efficiency.

But, when compression ratios were raised in the late 1940's (a trend
that continued in high performace cars in the USA until some cars has
12:1 compression)the old fashioned head gaskets *leaked*, so thinner
ridged gaskets were installed to make a better compression seal.

Thinner gaskets were part of the improvements necessary to use higher
compression ratios.

And, while higher compression ratios will increase low end torque and
make the engine "dig out" better from a dead stop, the engine will
reach its top RPM and stop revving.

It's a simple fact that if you increase the operating RPM by 50%,
you'll get 50% more power out of the engine. Yamaha has been a world
leader in advanced engine technology for years. When Toyota wanted an
advanced engine for a sports car they never actually produced, they
went to Yamaha for engineering expertise.

Yamaha discovered that they had two choices with the selection of
compression ratio in their 1980's cutting-edge technology 20-valve
Genesis motor. Yamaha's selection of 12:1 compression ratio initially
put me off on that design. I didn't realize that with all those valves
they had a lot of valve area at very low lift and they *needed* the
higher compression ratio. And the Genesis motor runs on regular
gasoline with 12:1...

Yamaha tested the genesis concept with 5, 7, and 9 valves per cylinder,
using single cylinder test engines to study the concept. They settled
on 5 valve per cylinder, 3 intakes, 2 exhausts.

Yamaha found they could run higher compression and have an engine that
accelerated well but wouldn't rev freely at the top end, or they could
use a slower-accelerating, lower compression ratio and enjoy the
benefit of more power at higher RPM *and* have an engine which could be
over-revved in a lower gear without the rider needing to shift gears.

That's why motorbikes like the Yamaha YZF-R6 have such stratospheric
redlines. The latest version has a 17.5K redline so the rider can use
2nd gear for most corners. What compression ratio does it have? I
dunno, and could care less. The R6 has just enough compression ratio to
avoid problems with *too much compression*!!!!!

The high RPM doesn't matter because the stroke is so short the engine
doesn't experience high piston speed and the rings are so thin (around
0.025") they have very little mass and are almost immune from ring
flutter as they experience plus and minus 4000 g's at the ends of the
stroke.

Back to your thinner head gasket notion. The deck height and connecting
rod stretch is critical on modern Suzuki engines. There is only about
0.010 squish clearance between the piston at TDC and the cylinder head.

Early SRAD GSXR's had problems with the pistons hitting the cylinder
head.

Suppose you did find a way to increase cranking compression and get a
big motor with a lot of "dig". What's it going to do to the rod
bearings, when you apply a lot of pressure on top of the pistons at low
RPM when the oil pump isn't making a lot of pressure?

Did you ever drive a car in the wrong gear and "lug" the engine?
Lugging is not the same as "bogging". The latter is when you operate
the engine at too low an RPM for the carburetion to work correctly.
Lugging is when you run the engine so slow the oil pump doesn't produce
enough pressure to float the crankshaft off the bearings. You hear a
buzzing sound and a vibration throughout the car.

Motorcycle oil pumps are intended to produce oil pressure at high RPM
and to get the oil up to the camshafts. Some drag racers would actually
install restrictors in the main oil gallery to redirect oil to the
camshafts, while risking oil starvation to the main bearings. My
GS-1100 has different oil pump drive gears to spin the oil pump faster
and produce oil pressure earlier.

If you're going to try to get more "dig", you need to think about what
you need to do with the oil pump. Will the turbo be running off of
engine oil pressure, at the expense of the camshafts and bearings?

You really need to think out what you're doing and why you're doing it
and understand the misconceptions of ignorant shade tree tuners before
you commit you time and money to a modification project. You could
avoid winding up with a pile of crap in your garage that resulted from
an ill-conceived modification project.

 

X
"Hmmm...it might be interesting
but I have been told by the commercial turbo-builders in Finland
that a supercharger would be much more expensive"

As you can see from my earlier post I live in Finland
My dictionary book is not in close reach
I'm not native English speaker,
so my technical vocubilarity is limited
that doesn't make me an idiot,
neither does your post with spelling errors make you an idiot
B-P
PS: thank you for understanding
what I explained with my limited English skills

 

I don't think you are really an "idiot". That was just a joke. And my
"spelling errors" weren't errors, they were an attempt to emulate the
regional dialect of the southern United States, where a lot of shade
tree mechanics build some very fast cars to race on dirt oval tracks.

But you won't gain any significant power by fitting a thinner head
gasket, you might just have the pistons hit the cylinder head, or the
valves will hit the piston and you have a badly damaged engine.

Modern Suzukis have too little clearance between the piston head and
the
combustion chamber to use the thinner gasket approach.

I've been hotrodding for over 40 years, and I learned the basics from
working around hotrodders that also worked on aircraft engines as well
as sportscars and motorcycles and "Detroit Iron", IOW, American V-8's.

Whether it's a 2-stroke, or a 4-stroke, the compression ratio is
selected to compensate for valve timing or port timing. The more
radical the valve or port timing, the more compression is needed to
compensate for it.

Slightly increasing the compression ratio by itself does very little
for an engine. Increasing the compression ratio radically reduces peak
power because the engine cannot breathe in fresh mixture at some
critical RPM.

I once milled 1/8th of an inch off of a Suzuki GT-750 3-cylinder
2-stroke engine's head in order to compensate for a wild port job. It
turned out that the available aftermarket pistons wouldn't work with
the crankshaft I had, so I wound up using the high compression head on
an engine with a far less radical port job.

All that happened was the engine had more low end power, but it
wouldn't rev up as high a the stock engine would rev. I sold that
motorbike to a guy who collected 2-stroke race bikes and he told me
that the head had far too much compression for the port job. I told him
that I knew that already.

 

X

Very informative, like your last post, thank you!

I think that it's better put my money on the new Kawa 1352cc
rather than boost up any other engines up to it's level
I is already designed have good torque at low rpm
[if one can believe the marketing]
while at the same time give enough horse power at high rpm
Brother-Peter
PS: My real name is Veli-Pekka
which is translated as Frere-Pierre [this time in French]

 

Peugeot JetForce Compressor - scooter with a supercharger. Power output
boosted from 12BHP to around 19BHP.

www.planetbikes.co.uk/peugeot_jet_forcecomp05.shtml

 

Cool!!!!