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Old 8th August 2015, 19:26   #76
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Default Re: Turbos on Indian off-road vehicles

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Originally Posted by ringoism View Post
just getting a good, guaranteed junkyard MDI-T for around 40,000 and selling off the MDI for scrap for several thousand is sounding like the better deal.

-Eric
No doubt about that!
Provided the motor is in decent condition, and it doesn't cause headaches when you go for RTO inspection.

How does that work these days by the way?
Back when I was last in India [nearly 10 years ago] I had to give up on my heavily modified RD350 because of that.
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Old 8th August 2015, 21:24   #77
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Default Re: Turbos on Indian off-road vehicles

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Originally Posted by ringoism View Post
Guessing more displacement means more air drawn in which would require a proportionate increase in fueling? (???)A "jerk" pump(???)
Jerk pump - the simplest of all the FIPs. So nothing to confuse us - get back to basics.

Next question: Suppose the jerk pump was perfectly setup for your original engine. Now you have bored and stroked your motor, but left the FIP part untouched. What results would you expect? In terms of power/ torque/ drivability, reliability, operating temperatures, smoke?

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Originally Posted by shashanka View Post
The only real "calibration" that can be done on
...
The rack position is effectively the throttle position.
Very correct, so brings me back to my original question

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Originally Posted by Sutripta View Post
Related- what exactly is meant by 'calibrating fueling' in a Bosch jerk injection pump? How is it done?
Because one comes across the term (increasing/ adjusting/ calibrating fueling) often enough on this forum.

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Sutripta
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Old 28th August 2015, 03:35   #78
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Default Re: Turbos on Indian off-road vehicles

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Originally Posted by shashanka View Post
The only real "calibration" that can be done on the Bosch helical groove plunger type pump is for the injection "cut-off" point. The injection cut-in point is fixed - in most plunger/barrel type Bosch pumps - since the top of the plunger covers the fuel inlet ports (nominal inlet pr. is usually 5-8 bar at booster p/p discharge) at a particular angle of the fuel cam travel (nominal value : 5 deg + - ~ BTDC).
The injection cut-off point is governed by the position of the helical groove which uncovers the same inlet ports, thus connecting the high pr. discharge side (250-350 bar in the pre-CRD engines) of the pump to the low pr (5-8 bar) fuel inlet side, thus theoretically cutting of injection instantly (again nominal value 7-10 deg + - ~ ATDC)
The position of the helical groove on the plunger vis-a-vis the inlet port is controlled by the rotary motion of the plunger which in turn is controlled by a rack & pinion arrangement. The rack position is effectively the throttle position. This relative position of the helical groove can be "calibrated", if you like, by dismantling the plunger/barrel and changing the relative meshing position of the teeth of the rack/pinion arrangement.
There was a later - though short-lived - modification to the Bosh pump by adding another helical groove to the top of the plunger, thus effectively controlling the fuel "cut-in" point also.
Oh my, I am just mind-boggled... I seriously want to get you up here to simply set my IP timing... amazing how many people around are servicing pumps, and that basically none of them know how to "correctly" set initial advance on a VE pump'ed engine. Pump guys tell me to give it to the mechanic, who will set it by ear. Might get it righter than we'd think that way, but still...

And I want to know why my MDI only runs right (have decent power and not miss badly at high rpm) when the pump is twisted to full-advance. Mechanic says there's a timing plate on the front side of the mounting that can be adjusted, having removed the front engine pulley/cover. Pump guy says no, there's an issue with the pump (low pressure on the vane side, maybe caused by leakage around the timing advance piston). I certainly don't know.


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Originally Posted by anjuna mark View Post
....headaches when you go for RTO inspection. How does that work these days by the way?
Really depends on the particular RTO, from what I hear. The last one I spoke with up here said it was no issue to put an MDI-TC engine in the Marshal. Just had to request permission in writing, and he'd grant it based on whichever clause / exception in the code was applicable. Asked an MVI I know in another state about converting the Impulse (150cc) to a Karizma 225cc engine, and he claimed it was possible to do legally. And my own heavily-modified enduro-style KB125 (gearbox, tyres, mudguards, handlebar, headlight, shockers/rear suspension, front forks, rear bodywork/taillight, etc) passed a few years ago, the only complaint from the MVI/RTO being that I didn't have turn indicators (he finally let it go on my assurances that "I would try" to get them installed). In that case, it might've been because none of them really knew what a 15-year-old "KB" was supposed to be like anyway. But I hear that a lot of local authorities are much more vigilant / unwilling to flex. I don't know how much leeway is written into the law, or how much "interpretation" is possible.

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Originally Posted by Sutripta View Post
Jerk pump - the simplest of all the FIPs. So nothing to confuse us - get back to basics.

Next question: Suppose the jerk pump was perfectly setup for your original engine. Now you have bored and stroked your motor, but left the FIP part untouched. What results would you expect? In terms of power/ torque/ drivability, reliability, operating temperatures, smoke?
More back on point here: Ahhh... googled it... so in common parlance you're speaking of an inline pump.

And now you want me to work out all these finer implications, when I've got a rotary pump... and two toddlers vying for my attention... Great questions to be sure, for which I hope to one day possess sufficient understanding to easily answer.

As an aside (but really fully back on-topic), a mechanic in Mandi whom I'd consider a good one told me today that it is very little trouble to just slap a turbo exhaust manifold and turbo on my non-TC MDI, for better power AND mileage (he says the fuel screw can be turned DOWN (???) which runs contrary to everything else I've read online). He hasn't personally done this, by the way, but seems to know of one or more persons who have.

Thanks,
Eric

Last edited by ringoism : 28th August 2015 at 03:43.
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Old 28th August 2015, 13:25   #79
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Default Re: Turbos on Indian off-road vehicles

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heavily-modified enduro-style KB125 (gearbox, tyres, mudguards, handlebar, headlight, shockers/rear suspension, front forks, rear bodywork/taillight, etc) passed a few years ago,
Eric
My go-to guy for RTO matters warned me not to bring my RD350 in at all. He said the regime was so strict, they'd take possession of the bike if I did.
It had [probably still has wherever it is] Honda xt550 front end and rear shocks, which gave it 14" ground clearance.
But I think the head of that RTO at that time was trying to prove how non-corrupt he was. I was told to garage the thing and wait until he was promoted or otherwise gotten rid of, after which traditional arranged flexibility would surely return.

Sure, you can save fuel by reducing the fuel... or just don't push the pedal all the way down for exactly the same effect.
It's not complicated, energy is produced by burning diesel fuel. if you can burn more, you get more energy. A turbo provides more air, giving you the possibility to burn more diesel.
Yes, there's a slight increase in efficiency, a couple of percent at best. So you could reduce your fuel 2% and end up the same as you were before spending all that money and effort.

One thing not mentioned [well maybe it was in the zillion pages of this thread] is the loss of engine breaking with a turbo conversion.
The turbo recycles some of the exhaust energy, letting the engine spin more freely. In the mountains this could be an issue, I've had trouble in the alps with a turbo diesel van.

Regarding engine durability;
if you double the rpm, the forces on the pistons, rods, and crank increase 16X.
If you double the power by turbocharging, the force increases 2X
If you reduce the rpm slightly and double the power, you won't increase the stress on those parts at all.
Heat is another story, but if you have an intercooler it should be ok.
Generally speaking, the gearbox, prop shaft, and rear diff will have no issue with a 50% increase in torque [note I'm not talking double now], but you will probably have to increase the force of the clutch pressure plate.
My clutch plate looked like a chapatti that had been forgotten on the fire.
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Old 28th August 2015, 21:00   #80
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Default Re: Turbos on Indian off-road vehicles

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Originally Posted by ringoism View Post
And now you want me to work out all these finer implications, when I've got a rotary pump...
But a diesel engine: the core of the questions. FIP type really does not matter for these questions.

Quote:
and two toddlers vying for my attention...
Diesel engines you'll figure out. But toddlers? By the time you figure them out, they'll be teenagers! And more fun that way.


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Originally Posted by anjuna mark View Post
Regarding engine durability;
if you double the rpm, the forces on the pistons, rods, and crank increase 16X.
??

Quote:
One thing not mentioned [well maybe it was in the zillion pages of this thread] is the loss of engine breaking with a turbo conversion.
You mean if Eric slaps a turbo on his Marshall, no other changes, engine braking will decrease?

Regards
Sutripta
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Old 28th August 2015, 21:35   #81
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Default Re: Turbos on Indian off-road vehicles

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Oh my, I am just mind-boggled... I seriously want to get you up here to simply set my IP timing... amazing how many

Thanks,
Eric
Ringoism dear chap,
No need to get "mind-boggled" about it, you know - just find yourself a marine engineer (there are enough of us around, & I'm sure Himachal has its share too), and if you asked him politely, I'm sure he'd help you out without breaking a sweat!
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Old 29th August 2015, 03:02   #82
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Default Re: Turbos on Indian off-road vehicles

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Originally Posted by Sutripta View Post


You mean if Eric slaps a turbo on his Marshall, no other changes, engine braking will decrease?

Sutripta
Yes.
However, that can be solved by adding yet another gizmo, an exhaust or "jake" brake.
Larger vehicles have them as standard, and for mountain descents on a light vehicle it would be a great help.
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Old 29th August 2015, 18:05   #83
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Default Re: Turbos on Indian off-road vehicles

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Ringoism dear chap,
No need to get "mind-boggled" about it, you know - just find yourself a marine engineer (there are enough of us around, & I'm sure Himachal has its share too), and if you asked him politely, I'm sure he'd help you out without breaking a sweat!
AFAIK, we are quite land-locked up here, and the only engineers who get near water are the hydel project guys...

But if I do somewhere in these hills eventually come across such a rare species, I'm going to try and bring him (or her?) home with me, bound and tied if necessary... (politely as possible, of course)

Of course, if you yourself would come willingly, be sure that I'll happily show you all around the place, practice good Indian hospitality, and not (literally, at least) attempt to hold you hostage.

-Eric

Last edited by ringoism : 29th August 2015 at 18:06.
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Old 29th August 2015, 19:02   #84
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Originally Posted by anjuna mark View Post
Yes.
However, that can be solved by adding yet another gizmo, an exhaust or "jake" brake.
Larger vehicles have them as standard, and for mountain descents on a light vehicle it would be a great help.

Sorry, but if everything remains the same why would the engine braking characteristics change?

Jeroen
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Old 29th August 2015, 19:17   #85
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Default Re: Turbos on Indian off-road vehicles

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Originally Posted by Sutripta View Post
You mean if Eric slaps a turbo on his Marshall, no other changes, engine braking will decrease?
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Originally Posted by anjuna mark View Post
Yes.
Could you pls. explain why. (Without complicating matters by introducing Jake/ Exhaust brakes.)
I am not asking for relative classification of engine type vs engine braking, where turbo diesels come at the bottom, and of which there should be thousands of web references, but of our (precise) question.

Similarly the engineering behind your "RPM doubled, forces 16X" statement.

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Old 29th August 2015, 19:53   #86
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Default Re: Turbos on Indian off-road vehicles

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AFAIK, we are quite land-locked up here, and the only engineers who get near water are the hydel project guys...
But if I do somewhere in these hills eventually come across such a rare species, I'm going to try and bring him (or her?) home with me, bound and tied if necessary... (politely as possible, of course)
Of course, if you yourself would come willingly, be sure that I'll happily show you all around the place, practice good Indian hospitality, and not (literally, at least) attempt to hold you hostage.
-Eric
Best of luck, old boy!
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Old 30th August 2015, 13:58   #87
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Originally Posted by Sutripta View Post
Could you pls. explain why. (Without complicating matters by introducing Jake/ Exhaust brakes.)
I am not asking for relative classification of engine type vs engine braking, where turbo diesels come at the bottom, and of which there should be thousands of web references, but of our (precise) question.

Similarly the engineering behind your "RPM doubled, forces 16X" statement.

Regards
Sutripta
The mathematics and engineering of crankshaft stress are far beyond my meager abilities to fully comprehend, let alone explain. It has to do with reciprocating mass, momentum, and velocity.
Nor can I tell you where I read it, as it was all long ago; probably in the afore mentioned book, "turbochargers".

The engine braking statement is based on my personal experience. I once had a Fiat diesel van, and then swapped it for an identical one with the same motor, but a turbo version.
There was a huge difference in engine braking. Descending long mountain roads with the turbo version was real hell, the engine would overspeed in 3rd, and I was forced o use 2nd and crawl all the way down.
This gave plenty of time to consider the engineering principles of engine braking.
What we're trying to do is dissipate stored energy, in the case of a descent, the potential gained during the accent. If the vehicle is heavy, there is a lot of energy to dispose of. The brakes overheat within a few minutes [all mountain drivers know this].
The engine is normally used as a brake, because it has a large cooling system that can handle the heat.
The energy we need to lose is in each meter of descent, so at a higher speed it's more energy per second. If the engine can't offer enough resistance, it will overspeed forcing either brake use [have you ever seen smoke rising from your brakes? I have] or changing to a lower gear and lower vehicle speed, until the energy per second is reduced to a level that engine resistance can equal on a continuous basis.

The turbocharger is spinning along with the engine, pushing air past the intake valves, pushing the pistons down. It is efficiently recycling some of that energy that in this instance, we want to get rid of. The engine gains far more energy from the pressurized intake air than it loses from the very slight increase in exhaust back pressure [that part is from the book].

My Swaraj Mazda had an exhaust brake as standard, and I didn't make any measurements of engine braking effects before or after the turbo conversion. But it felt ok in practice.
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Old 30th August 2015, 21:41   #88
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Default Re: Turbos on Indian off-road vehicles

^^^
Lets wait for the opinions of the more learned/ engineers on this site.

Suffice it to say I don't quite agree with the two statements (RPM-Force, and Turbo-Engine Braking).

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Old 31st August 2015, 09:18   #89
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^^^
Suffice it to say I don't quite agree with the two statements (RPM-Force, and Turbo-Engine Braking).
I agree with you not agreeing to either statement.

Jeroen
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Old 31st August 2015, 18:02   #90
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I agree with GTO .........There are times when I am using gears to slow down in my Diesel swift and the turbo kicks in.
I agree with GTO on getting a bigger engine rather than a turbo.
GB
Hi GB, I dont get this - do you mean that the Swift has a thresh-hold engine rpm at which point the t/charger is allowed to start revolving?
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