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Electric. Digital. Computerized. Throttle Body Sync


Du-Rron

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This post got me thinking about the 'SVTC. I looked through the manual and found nothing about syncing the throttle bodies. Will look again but I looked pretty good.

 

There is no requirement for throttle body sync on the VN900 either, but, the ports and the air screws are there.

 

vn900body.jpg

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This post got me thinking about the 'SVTC. I looked through the manual and found nothing about syncing the throttle bodies. Will look again but I looked pretty good.

 

Ooops... unlike the VN900, the #1 reason why the SVTC does not require a throttle body sync is... IT ONLY HAS ONE THROTTLE BODY.

 

th.jpg

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  • 4 weeks later...

Hi guys

 

Vacuumate has been and can do both without the headaches of electronics.

 

But this fellow only has a new toy and is using it as a toy. His doubt about the valve lash was answered so why sync? If we sync to unequal valve air flows then we dumb the rest down to mimic the bad one (s)

 

Just sayin ;)

Patch

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I had a twin-max digital for years in the shop that we LOVED because of it's precision. It was very accurate and I was always amazed at how, after syncing with mercury or vacuum gauges then following up with digital the digital showed inaccuracies of the others.. GREAT for that finish fine tune IMHO.. GOOD find Duey!!:thumbsup:

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Hi guys

 

Vacuumate has been and can do both without the headaches of electronics.

 

 

Vacuumate $650.00 Healtech $350.00

 

But this fellow only has a new toy and is using it as a toy. His doubt about the valve lash was answered so why sync? If we sync to unequal valve air flows then we dumb the rest down to mimic the bad one (s)

 

Patch

 

Huh?!? Whatnow?!? SayWhat?!?!

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Huh?!? Whatnow?!? SayWhat?!?!

 

 

What Don said is correct and the theory applies broadly across naturally aspirated engines.

 

Whether you are F.I. or Carb the process of syncing throttles is a matter of volume and velocity balance.

F.I. will deliver a programmed fuel pulse (adaptive or not), and carburetors will siphon and atomize fuel.

So equalized volume and velocity at the throttle is the task being attempted and is what we are reading via vacuum measurements regardless of tool used.

If as he suggest there is doubt over lash then the sync is not balanced because the process is not an individual one, each individually adjusted body affects the other to work as one team.

I’ll go a little deeper: When lash is out of spec the valve stroke and duration has changed. This means that volume and velocity has also changed and that means jug to jug efficiency has also changed!

When we sync as shown (just the intake side of the equation) and the valve strokes are not corrected then @ WOT (for example) are all throttles at 90*? Or at 4000 rpm.. are they close to equal? (Volume wise) remember that is the task.

Ask why the book calls for maximum pressure differentials and minimum pressure potentials? They build volume and velocity base lines. If we ignore the valve duty cycles then we also accept that regardless of intake feed efforts, combustion efficiency may or may not be close enough to produce good throttle response, period because, the volumes and velocities are not as expected: therefore combustion pressures applied to the crank are also less than expected regardless of potential displacement designed efficiencies.

Consider this; displacement potential can only be converted to torque after the process of first getting the air/fuel ratios in past the throttles and intake valves… Each link in the change applies forces to the crank; each jug that is lower in fill % is lower in output. This means that syncing the bodies or equalizing them while the valve train is out of spec results in an invalid sync, in fact dumbs the performance poetical.

 

The tool while likely a good investment for a mechanic or serious new comers to the sport is designed around the principles that in this case sound like were ignored.

 

My reference to the vacuummate is simply that the strobe side of it tells you at a glance if it is sensing incorrect pressures form either side of the valve train which means - correct before proceeding to sync.

 

Anyways just an opinion

Patch

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Huh?!? Whatnow?!? SayWhat?!?!

 

 

What Don said is correct and the theory applies broadly across naturally aspirated engines.

 

Whether you are F.I. or Carb the process of syncing throttles is a matter of volume and velocity balance.

F.I. will deliver a programmed fuel pulse (adaptive or not), and carburetors will siphon and atomize fuel.

So equalized volume and velocity at the throttle is the task being attempted and is what we are reading via vacuum measurements regardless of tool used.

If as he suggest there is doubt over lash then the sync is not balanced because the process is not an individual one, each individually adjusted body affects the other to work as one team.

I’ll go a little deeper: When lash is out of spec the valve stroke and duration has changed. This means that volume and velocity has also changed and that means jug to jug efficiency has also changed!

When we sync as shown (just the intake side of the equation) and the valve strokes are not corrected then @ WOT (for example) are all throttles at 90*? Or at 4000 rpm.. are they close to equal? (Volume wise) remember that is the task.

Ask why the book calls for maximum pressure differentials and minimum pressure potentials? They build volume and velocity base lines. If we ignore the valve duty cycles then we also accept that regardless of intake feed efforts, combustion efficiency may or may not be close enough to produce good throttle response, period because, the volumes and velocities are not as expected: therefore combustion pressures applied to the crank are also less than expected regardless of potential displacement designed efficiencies.

Consider this; displacement potential can only be converted to torque after the process of first getting the air/fuel ratios in past the throttles and intake valves… Each link in the change applies forces to the crank; each jug that is lower in fill % is lower in output. This means that syncing the bodies or equalizing them while the valve train is out of spec results in an invalid sync, in fact dumbs the performance poetical.

 

The tool while likely a good investment for a mechanic or serious new comers to the sport is designed around the principles that in this case sound like were ignored.

 

My reference to the vacuummate is simply that the strobe side of it tells you at a glance if it is sensing incorrect pressures form either side of the valve train which means - correct before proceeding to sync.

 

Anyways just an opinion

Patch

 

Another excellent read written by the Master Of Machine IMHO. Another issue associated that one may want to consider in the classroom of thought when talking proper valve lash concerns that I have bumped into is that as a valve face wears it naturally closes the valve stem height = the need for lash adjustment is urgent. Most non hydraulic lifter valve lashes are set somewhere like 3 thou for the intakes and 5 for the exhaust valves. This .003 or .005 (your factory specs may differ) is not a lot of wear room before the lash crosses into the 0 or -0 zone allowing for compression necessary for combustion to drop significally as the valve no longer seals on the seat properly. A concern then can come into play as it is possible to actually burn valves (this concern is more common on exhaust valves from what I have seen).

 

GREAT to have you back in front of the class Teach!!:bowdown:

Puc

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It's for synching the throttle bodies of a fuel injected bike. That being said, I don't know why it wouldn't work. You are still working with vacuum. I synced the throttle bodies on a BMW with my Carbtune. Same thing.

 

Huh?!? Whatnow?!? SayWhat?!?!

 

 

Im still trying to figure out, "What Don said..." and where in this post he said it. :think:

 

 

:think::think:

 

:think::think::think: and a double :scratchchin::scratchchin:,,, as usual, I think my post may have cornfused even me cause a [ ] or two got chopped somehow.. Twasnt I who

quoted Don,, twas Patch.. That being said, I got a hunch that he was talking about the "what Don said" in the posted I quoted above... Ohhhh Lord help me if I spoke for Patch and am wrong :crackup::crackup::crackup:There'll be no little stars on the top of this lop eared Grasshopper varmints home work if I am I tell ya :buttkick::smash2:

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Good write up Steven G. It was actually quite a refresher as despite being a Mechanic for 45 years you brought up a reminder of a few things I have not thought about for years since valve train issues are not as common an issue these day's among big trucks and even cars as they once were. And usually when they do become an issue they are rarely small ones but pretty devastating.

 

However when syncing carbs I would be inclined to think any cylinder with a valve issue would show an unstable or excessively low vacuum reading versus the other cylinders.

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:think::think::think: and a double :scratchchin::scratchchin:,,, as usual, I think my post may have cornfused even me cause a [ ] or two got chopped somehow.. Twasnt I who

quoted Don,, twas Patch.. That being said, I got a hunch that he was talking about the "what Don said" in the posted I quoted above... Ohhhh Lord help me if I spoke for Patch and am wrong :crackup::crackup::crackup:There'll be no little stars on the top of this lop eared Grasshopper varmints home work if I am I tell ya :buttkick::smash2:

 

 

Hmm now I confused again lol at least I know why:)

 

So Don has been right before?

 

Thanks Puc for putting it together!

 

It will be a while before I can back track and pin down things that seem right there but maybe aren't.

Till then its just what's in my ram that I can count on and that too is limited at the moment.

 

Patch

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:think::think::think: and a double :scratchchin::scratchchin:,,, as usual, I think my post may have cornfused even me cause a [ ] or two got chopped somehow.. Twasnt I who

quoted Don,, twas Patch.. That being said, I got a hunch that he was talking about the "what Don said" in the posted I quoted above... Ohhhh Lord help me if I spoke for Patch and am wrong :crackup::crackup::crackup:There'll be no little stars on the top of this lop eared Grasshopper varmints home work if I am I tell ya :buttkick::smash2:

Wow @cowpuc you really out did yourself this time usually you just confuse everyone else :confused07::starz::think::puzzled:....but to actually confuse yourself. Thats a whole new level :bowdown:
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Wow cowpuc you really out did yourself this time usually you just confuse everyone else :confused07::starz::think::puzzled:....but to actually confuse yourself. Thats a whole new level :bowdown:

 

The more geezerly I get,, the more well defined the term "confused" becomes Bum :missingtooth:

 

I always stay in a state of mass confusion unless I am at the range and then all comes into clarity.

 

:farmer:

 

I am SOOO right there with you my eternal brother Sly!! :thumbsup::thumbsup::big-grin-emoticon:

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Good write up Steven G. It was actually quite a refresher as despite being a Mechanic for 45 years you brought up a reminder of a few things I have not thought about for years since valve train issues are not as common an issue these day's among big trucks and even cars as they once were. And usually when they do become an issue they are rarely small ones but pretty devastating.

 

However when syncing carbs I would be inclined to think any cylinder with a valve issue would show an unstable or excessively low vacuum reading versus the other cylinders.

 

 

All right good point, so sticking to the fresh side and NO plenum.

 

So in the above we assume negative lash. Not too dissimilar to what Puc was suggesting.

 

Here a trained ear will provide the shortcut but how would we set the benchmark to know lash verses Puc's burnt valve potential if dealing with intake side.

 

The easy out here is of course the jug pressure which should measured first in all cases. But lets follow the trail you lay it out:

Lets choose an easy bench, say 100psi. #2 is consistently 90 psi or 10% low 1,3&4 are within 3to4% +/- just to set the scenario.

 

#2 appears to show a minor leak, lash, crack (s) or seat,, all 3 could be the cause but only one is correctable without head removal. So when we think to solve the issue via lash adjustment we consider stretch or ware and both have room for compensation. Points of ware can also be from the lobe, right.

 

If the stem has stretched regardless of type of adjustment we reduce (stating the obvious) but why am I not simply just answering the vacuum question? Well because in this case the problem is obvious. No plenum so each compression stroke produces pressure leakage thru the carb body! This shows on the gauge via shaky needle so that would be the answer.

 

But not helpful for the less experienced fellow using a merc stick right. And for that reason ignoring the pre-steps to carb syncing produces bad results, just as bleeding a stick to compensate say for the lack of a throttle bench sync after a cleaning or rebuild! Yet how many tune the sticks without knowing the potential you mention above?

 

Summing up, syncing the bodies is the last step before the final idle & idle circuit mixture; the real work are the steps preceding the sync! In my witness to to too many threads in many forums the steps mentioned above are ignored or happen in reverse, if at all!

Edited by Patch
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