Timing belt

[JoshMc]

I don’t really understand what the question is but I will try to explain what I think you are asking about.

The camshaft / camshafts are driven by gears from the crankshaft to control the opening and closing of the intake and exhaust valves to direct the flow of fuel / air mixture into the combustion chambers and the flow of exhaust gasses out of the combustion chambers at very precise times in the engines operating cycle. This operation is sometimes adjusted to ” tune ” the engines performance for a specific RPM or condition such as for example supercharging the intake air supply. This tuning if done properly can increase the power that the engine produces but usually causes adverse effects for normal use so is generally left for purpose built race vehicles. When an engine is modified in this manner it usually requires a premium fuel because the ignition system has to be very precise to prevent detonation of the fuel mixture prematurely. Since premium fuels ignite very consistently the engine can burn the fuel at it’s peak levels to squeeze more power from the available displacement. This is why factory super cars require premium fuels as well.

If this mechanic was putting the engine back to original equipment specifications because the belt jumped a tooth I can understand the reason. If it was done to try to increase the vehicles performance I would be very concerned because the original design of the timing system rarely if ever has the type of precision equipment needed to make these changes safely. I would ask your mechanic for details on why the change was made or if it was correcting an issue.

Topic

[umerrauf]

Thanks 4 a reply… actually i asked my mechanic that my car pick is not good and it doesnt accelerates when i press accelerator . he checked all the tuning stuff like tappet , plugs and fuel adjustments and at last he remove the timing belt and move the cam one step forward from the arrow direction mentioned, towards the bumper. and the he again put the belt . he sets the timing on 18 and iam confused that all these changes would not effect badly my cars engine.

[dreamer2355]

It sounds like they may be advancing or retarding the mechanical timing for some unknown reason._x000D_
_x000D_
Each vehicle has timing marks that should line up when the engine is at TDC. Any change to this will effect the performance of the vehicle.

[umerrauf]

Thanks… I have suzuki Alto vxr with engine having 8 valve and 4 piston. I have checked Tappets, plugs and also the timing belt changes and i have told in above post… but still my car has a bad pick at patrol…… when i force the accelerator down the car instead of accelerating goes down …..i have also check the clutch plate and pressure plate and it is ok…… Also i have check the compression test. and it is ok….. Please advice what will be the cause of a bad pick and car is not going above 70km/hr….

[umerrauf]

Mechanic did this for a good pick

[dreamer2355]

You need to make sure the engine is in correct mechanical timing before proceeding.

Did you make sure the timing marks are correct?

Or just find a qualified certified technician to work on your vehicle as there should be no need to adv/retard stock base timing on a non performance vehicle.

[EricTheCarGuy]

Adjusting cam timing is not something that I recommend but it is done, in fact they make special cam pulleys that do that very thing and allow you to adjust the cam timing. What you’re doing is moving the power curve of the engine closer to the bottom of the RPM range. Every engine works best during a given RPM where it produces the most power, most engines do this around 2500-7000 rpm. Once you reach a certain point power begins to drop off due to the mechanical limitations of the engine. You CAN move the power curve closer to the bottom end of the RPM range by ‘advancing the cam’ as your mechanic did. On modern vehicles without making corrections for the computer controls this can prove problematic however as the computer may try to correct for the advanced timing and performance may be compromised as a result.

[umerrauf]

I have checked the timing marks and they are correct… car is not moving above 60 km/hr.

[umerrauf]

My car rpm is good at idle and getting a good race when i put a foot on accelerator but when i put it in gear and on road it is not going above 60km/hr. Please advice what is the problem.

[ytram]

[quote]Quoted From umerrauf: _x000D_
_x000D_
My car rpm is good at idle and getting a good race when i put a foot on accelerator but when i put it in gear and on road it is not going above 60km/hr. Please advice what is the problem.

[EricTheCarGuy]

I know you say you checked the timing marks but if the cam is advanced the power curve will drop off sooner than stock and would be the most likely cause of that performances issue.

[Author]

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