How A CDI Works (Gen 1) - Page 3 - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #21 of 34 Old 09-21-2014, 09:08 PM
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Now, we all know that there has never been a dyno result that was significantly off, don't we?

"It's still unsolved", Tom said mysteriously.

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post #22 of 34 Old 09-22-2014, 06:42 AM Thread Starter
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Quote:
Originally Posted by Tom Schmitz View Post
Now, we all know that there has never been a dyno result that was significantly off, don't we?

"It's still unsolved", Tom said mysteriously.

Tom
Well, the dynamometer charts from the PCV valve mod installation were certainly valid and accurate.

Weren't they?

I mean, WEREN'T they?

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post #23 of 34 Old 09-22-2014, 12:36 PM
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I have addressed this several times. It works for the KLR + several ATV's and many/most late 1970's & 1980's US V8's, for the same reason. Whether one understands an effect has no bearing as to its efficacy. In fact, we often explain empiracal factors by applying faulty theory which isn't recognized because we do not test the explanation. We do this all the time in the course of day to day. "Hindsight has 20/20 vision" expression is a perfect encapsulation.

Cams retarded the exhaust timing in order to increase combustion burn time because of the need to reduce CO levels. It was the most practical means of addressing the problem at that time of engine development. As for the valve timing numbers so favored by people who read articles but haven't worked with camshafts, IME they are virtually valueless excepting in a very broad sense. One has to actually try the cam grind in the engine configuration in question to determine how well it will work. Grind the same profile onto a 351W and 350 small block GM and they will often be significantly different in utility. I learned that early on from Barry Shadbolt when in the marine business. Each and every opportunity to verify has shown him to be correct as one would expect because one doesn't reach that level of international respect by being off track.

Dyno results are often not reflecting what is represented, incorrectly reported, or "optimistic". They also aren't of much value in isolation or compared with another dyno's numbers because few dynos are accurately checked. For the purposes of diagnosis or tuning, one really doesn't care much about the numbers but rather simply the effects of load and/or the improvement shown. People were always hounding me to run their car on the dyno but why? Having a rear wheel torque doesn't make the thing faster.

Running the engine on a specific dyno while comparing the effects of various changes can be extremely effective but as Tom alluded, one can be wrong for many reasons. Skepticism is always in order.

I'd have to observe the PCV dyno results to accept the claims. Perhaps we can watch together, Tom? ;-)



Quote:
Originally Posted by Damocles View Post
Simply advancing the exhaust cam one cam sprocket tooth subtracts 15 crankshaft degrees of valve overlap.

I don't understand how jettisoning valve overlap produces the claimed 10 % horsepower increase across the rpm spectrum. Don't deny it's there, just wonder how it's produced. Most (if not all) "performance" cams have increased valve overlap, not reduced (compared to stock).

Automobiles with "variable valve timing" advance BOTH intake and exhaust valve timing with rpm, not just the exhaust valve timing alone. Kawasaki advanced both intake and exhaust valve timing on its V-twin ATV engines, transitioning from utility to sport models, moving the horsepower peak upward, rpm-wise.

I'm sure men of good will conscientiously performed the "MC Mod" experiments, but if only a slight gain was measured, I'd wonder at the accuracy/precision/repeatability error budget of the dynamometer involved.

---------------------------

I imagine spark advance is determined by the pulse rate of the pickup coil output. I don't cognate the "air gap" considerations mentioned; don't know where the air gap might be located, its significance, or its adjustability; but . . . that's just ME!
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post #24 of 34 Old 09-22-2014, 02:04 PM Thread Starter
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Originally Posted by Normk View Post
I have addressed this several times. It works for the KLR + several ATV's and many/most late 1970's & 1980's US V8's, for the same reason. Whether one understands an effect has no bearing as to its efficacy. In fact, we often explain empiracal factors by applying faulty theory which isn't recognized because we do not test the explanation. We do this all the time in the course of day to day. "Hindsight has 20/20 vision" expression is a perfect encapsulation.

Cams retarded the exhaust timing in order to increase combustion burn time because of the need to reduce CO levels. It was the most practical means of addressing the problem at that time of engine development. As for the valve timing numbers so favored by people who read articles but haven't worked with camshafts,
"Cams retarded the exhaust timing in order to increase combustion burn time because of the need to reduce CO levels. . . . "

REALLY, Normk? Not according to the camshaft timing specifications, from 1987 to 2014, I think. Do you have contradictory data?

If so, WHEN did Kawasaki retard the cam timing on the KLR650 engines? I didn't think they EVER did, from 1987 to the present.

I don't think I qualify as, one of those you refer to as "people who read articles but haven't worked with camshafts." While I would not pretend to be an Ed Iskenderian or a Smokey Yunick, I've degreed and set up a camshaft or two in my checkered and largely wasted past. I have personally dealt with WEBCO (camshaft grinder) before they became WebCam. Yet I defer to your unimpeachable internal combustion engine technical knowledge and expertise.

Now lets look at some of those "figures," which you apparently minimize and dismiss, at least to some extent:

KLR650 exhaust valve timing:

EV opens 57 degrees BBDC
EV closes 31 degrees ATDC

NOTE: Generation 1 data.

With the "MC mod," the Generation 1 exhaust valve timing would be:

EV opens 72 degrees BBDC
EV closes 16 degrees ATDC

(Notations in CRANKSHAFT DEGREES, conventional practice regarding valve timing.)

Now, what is the stock exhaust valve timing on Generation 2s?

If significantly retarded from Generation 1 STOCK exhaust valve timing, I shall humbly stand corrected, and shall note as 2008 the model year when Kawasaki retarded exhaust valve timing, allegedly "to reduce CO levels," an allegation without citation. Maybe so, but . . . I'd appreciate an authority beyond what some uninvolved person posted on an Internet website.

DISCLAIMER: I'm NOT suggesting advancing the exhaust valve camshaft 15 crankshaft degrees does NOT produce an extra 10 % power output across the rpm spectrum, as claimed; I just wonder . . . HOW?

Last edited by Damocles; 09-22-2014 at 02:07 PM.
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post #25 of 34 Old 09-22-2014, 03:23 PM
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Please re-read what I have said so many times. We are simply not communicating.
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post #26 of 34 Old 09-22-2014, 05:40 PM Thread Starter
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Please re-read what I have said so many times. We are simply not communicating.
I have re-read what you have said, many times, Normk!

And, I suppose I must agree with you, we are simply not communicating!

I've asked HOW advancing an exhaust cam 15 crankshaft degrees produces more power. You decline to discuss the mechanism (seems to me), instead stating as a FACT Kawasaki retarded valve timing for emissions purposes, sacrificing power, but . . . offer no provenance, no proof, no citation, no credible reference substantiating your allegation. May be so, but . . . where's the evidence?

I point out the stock exhaust valve timing, which as far as I know, hasn't been "retarded" for 27 inclusive model years (since 1987); I ask you to provide evidence exhaust valve timing has been retarded. No response, other than declaring valve timing specifications/data are essentially meaningless, in the arcane world of valve timing.

Conceivably, Kawasaki has been compromising power by retarding exhaust valve timing since 1987 for emissions purposes; if so, I'd expect the practice to be documented, somewhere. Generally, I think emission requirements were much looser in 1987 than presently.

On the contrary, I think IF advancing exhaust valve timing (ONLY) increases power output, a credible and plausible explanation exists for this result. Further, in my opinion, valve timing specifications have a useful place in engine design and tuning. My opinions, only. I respect yours.

=============

For some additional dimension in the discussion, does someone have a service manual with stock valve timing specifications for Generation 2s?

If so, please share exhaust valve opening (XXX degrees BBDC) and closing (XXX degrees ATDC) data.

Thanks!
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post #27 of 34 Old 09-22-2014, 05:49 PM
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Quote:
Originally Posted by flash View Post
Looked again and it was in the General Information section of the factory manual.
There is a difference....

Exhaust opens 57 degrees BBDC
Exhaust closes 37 degrees ATDC
Duration 274 degrees

...
Flash found it a while back.

Thus the Gen 2 MC Mod results in:

Exhaust opens 72 degrees BBDC
Exhaust closes 22 degrees ATDC
Duration 274 degrees

Compare and contrast:
Quote:
Originally Posted by Damocles View Post
...

KLR650 exhaust valve timing:

EV opens 57 degrees BBDC
EV closes 31 degrees ATDC

NOTE: Generation 1 data.

With the "MC mod," the Generation 1 exhaust valve timing would be:

EV opens 72 degrees BBDC
EV closes 16 degrees ATDC

(Notations in CRANKSHAFT DEGREES, conventional practice regarding valve timing.)...
HOW it works I cannot say with certainty, though I might guess that if the exhaust is closed earlier relative to the intake, that the intake charge would have a greater opportunity to fill, as it is not competing with exhaust pressure. On the other hand, it might be thought that advancing the exhaust valve timing would rob the intake of the benefit of the exhaust gas being expelled, which would tend to pull the intake gasses in and result in a fuller charge of air/fuel. It could be either one of these, or several other options that I'm not even able to think of as they are well beyond my ken.

Since both of those scenarios can be argued (in my split-level head) equally, I guess I'd have to shrug and offer "There are more things than valve timing going on here and the effects of those things are hard to argue on paper", Tom said dynamically.

Some of those things might be charge velocity, port shape, combustion chamber shape, internal head volume, etc.

I think the last time we looked at this, we also looked at the intake timing and the overlap. I have to wander back and look at that.

Tom

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Last edited by Tom Schmitz; 09-22-2014 at 06:07 PM.
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post #28 of 34 Old 09-22-2014, 06:49 PM
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In my understanding only,
Kawasaki Did Not Advance nor Retard the exhaust cam Timing on the Gen 2 or E series KLR for the 2008 and up years.
They Extended the Closing Ramp of the exhaust cam lobes, which Increased the Exhaust cam Duration and therefore Extended the Over-lap Duration.

As little as I understand hi-performance tuning vs low end Torque tuning, I'll try to give my understanding of the MC Mod.

By Advancing the exhaust cam only, we open the exhaust valves earlier and more importantly Close them Earlier.
By closing the exhaust valves Earlier, we get a Stronger Intake 'draw' or pulse.
By getting More Intake at a Lower rpm, we get a 'Torqueier' engine at lower rpm, but we May sacrifice some peak rpm potential and therefore peak HP.
IMU,only.

As Normk found on his personal Gen1 or A series, They Do Not all respond in the same manner. Probably due to mass production tolerances.

Just my understanding, guys .

pdwestman
Modify at "YOUR OWN RISK"!

Still riding my 1987 KL650-A1. 84,000+ miles & counting
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post #29 of 34 Old 09-22-2014, 07:11 PM
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I am also not able to offer more than to state what happens when valve timing is changed in a large variety of engines. I never intended to imply that Kawasaki offered one valve timing for the KLR and subsequently retarded that timing.

Just so we're clear, I'm not throwing stones so if it appears that way, that is not my intention. From working with marine and automotive engines from before and through the early emissions period, I observed several changes in valve timing which were directed to reducing emissions. That is what I stated and hope that have made this clear.

To return to my earlier example, if one were to take a pre-emissions Ford 429 engine, for example, the cam timing placed the index in line with the flywheel key. One can verify this with dial gauge as have done many times. When the 460 came under emissions (460 and 429 are almost identical), the noticeable change was that the cam index was placed 1/2 crankshaft tooth = 1 camshaft tooth ahead of the flywheel key. This retarded the valve timing by one camshaft tooth.

It was common practice for us to use a 429 timing set or to simply advance the camshaft of 460's by one camshaft (chain) tooth in order to "return" the cam timing to the pre-emissions point. This had the effect of increasing engine torque throughout the RPM range which also resulted in much better fuel consumption. We always had to reduce both curb (warm) idle and fast (choke) idle speeds following this modification which also indicated increased efficiency since idling at the same speed with smaller throttle opening (less air) can only come from improved efficiency.

Reflection as to the rationale for retarding (opening exhaust valves later) the timing will indicate that this increases the burning time for the combustion charge which will allow additional time for burning of partially burned fuel or CO. Running exhaust gas analyzers mapped this effect which was why some jurisdictions could not get through testing with the cam advance unless other things were done.

Checking with tune-up and emissions schools agreed with the scenario.

These effects were also seen virtually across the board with US engines of that era.

As I have said, it seems reasonable that Kawasaki followed the same course in developing cam timing which provided appropriate output, then finding that CO was high, were forced to increase burn time by the only practical means which was by opening exhaust valves later.

The KLR engines in which I have advanced cams (both Gen1 & Gen2) behaved as do various V8's and a number of ATV and other engines.

I have not run one on a gas bench but would bet a some donuts that taking an optimized air-fuel ratio KLR with advanced cam timing and comparing with retarded cam timing (exhaust) will see CO climb beyond the emissions limit.

Don't have to be right about this, simply offering the only case I have seen to explain the timing and rationale. If there's a better answer then I'd like to hear it as that would be interesting and possibly point to some opportunity.

Throwing valve timing numbers around without any justification as to their applicability is simply not useful. We saw many examples of the engineers not being able to predict the effects of various cam profiles to a useful degree. If they couldn't use these numbers to predict effects to a useful degree.....

We do know:

1) The KLR has been subject to emissions standards in some markets.
2) The reaction to advancing the exhaust cam is similar to other engines subject to emissions.

So, failing it seems reasonable that the pattern fits.

In fact, increasing emissions levels have apparently encouraged the addition of exhaust air "injection" which would serve to reduce CO and possibly HC levels.

I'm done with this subject because it seems only to go round and round. Perhaps that's my doing and if so I apologize for the band width.
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post #30 of 34 Old 09-22-2014, 09:12 PM Thread Starter
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Thanks for the Generation 2 valve timing info, Tom Schmitz!

Generation 1, EV open 57 degrees BBDC; close 31 degrees ATDC, 268 degrees duration.
Generation 2, EV open 57 degrees BBDC; close 37 degrees ATDC, 274 degrees duration.

Thus it appears the exhaust valves stay open longer, close later in the cycle, with Generation 2 vs. Generation 1 (by 6 crankshaft degrees, the amount the duration was extended). Exhaust valves open at the same point for either generation.

Don't understand how leaving the exhaust valves open longer reduces environmental pollution, but by some complex interactive relationships, perhaps this is so.

And, advancing the exhaust valve timing 15 crankshaft degrees while subtracting 15 crankshaft degrees from valve overlap may indeed deliver a 10 % power increase across the rpm spectrum.

Regardless, I appreciate the conscientious effort to explain how this might be the case, from those who have discussed the issue on this thread. Thanks for the interesting possibilities raised, guys!

Last edited by Damocles; 09-22-2014 at 09:24 PM.
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