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Search found 3137 matches

by David Redszus
Tue Jan 26, 2021 2:07 pm
Forum: Engine Tech
Topic: valve spring open pressure
Replies: 18
Views: 824

Re: valve spring open pressure

"For a given valve spring rate, the spring force will increase proportional to lift. A doubling of lift will double the force exerted by the spring." This is only true when the spring is installed with with zero force at zero lift. Loading the spring at zero lift introduces an "offset" into the lif...
by David Redszus
Tue Jan 26, 2021 1:35 pm
Forum: Engine Tech
Topic: Lighter valve train
Replies: 16
Views: 943

Re: Lighter valve train

imagine a case where you have adequate force "over the nose" but the spring is installed without any preload and therefore the force on the seat is effectively zero. How well do you think that will work for preventing bounce? The parameters that affect valve spring selection and tuning are: spring ...
by David Redszus
Mon Jan 25, 2021 9:37 pm
Forum: Engine Tech
Topic: Lighter valve train
Replies: 16
Views: 943

Re: Lighter valve train

imagine a case where you have adequate force "over the nose" but the spring is installed without any preload and therefore the force on the seat is effectively zero. How well do you think that will work for preventing bounce? The parameters that affect valve spring selection and tuning are: spring ...
by David Redszus
Sat Jan 23, 2021 2:41 pm
Forum: Engine Tech
Topic: Lighter valve train
Replies: 16
Views: 943

Re: Lighter valve train

Valve spring seat force has nothing to do with engine rpm. It can ... if valve bounce is an issue; as pointed out earlier. I'm afraid the problem is a bit more complex. Ignoring valve train mass and engine speed for the moment. Using a constant lift, spring rate, and spring free length, the seat fo...
by David Redszus
Fri Jan 22, 2021 1:34 pm
Forum: Engine Tech
Topic: valve spring open pressure
Replies: 18
Views: 824

Re: valve spring open pressure

Every cam mfg can provide a lift curve with one degree increments. If he want to. Many do not. With an accurate lift curve, cam lobe velocity, acceleration, and higher derivatives can be calculated. But, what is needed is actually a valve lift curve. Now we can calculate valve acceleration, which wh...
by David Redszus
Fri Jan 22, 2021 10:26 am
Forum: Engine Tech
Topic: valve spring open pressure
Replies: 18
Views: 824

Re: valve spring open pressure

Software is just a prediction, real world can be different and usually is. Valve float prediction software can be very accurate...statically. I have written such a program. But real engines operate in a dynamic world which is not as nice and smooth as are equations. The problem becomes a matter of ...
by David Redszus
Thu Jan 21, 2021 6:11 pm
Forum: Engine Tech
Topic: Lighter valve train
Replies: 16
Views: 943

Re: Lighter valve train

Hi all, i have located a cam lifter that are 30 grams less ( 53g total weight). I’m thinking of running less valve seat pressure to free up more horse power. These motors (spec formula single seaters) i build are flat fours with a lifter, push,rocker assembly. My seat pressure is 68 lb as these thi...
by David Redszus
Thu Jan 21, 2021 3:34 pm
Forum: Engine Tech
Topic: valve spring open pressure
Replies: 18
Views: 824

Re: valve spring open pressure

For a given valve spring rate, the spring force will increase proportional to lift. A doubling of lift will double the force exerted by the spring. But, for a doubling of rpm, the valve acceleration G force will quadruple; increase by a factor of four. While maximum spring force is reached at maximu...
by David Redszus
Thu Jan 21, 2021 11:14 am
Forum: Engine Tech
Topic: valve spring open pressure
Replies: 18
Views: 824

Re: valve spring open pressure

Spring PRESSURE is an incorrect term. We should be considering the required spring FORCE. Seat force is required to adequately seal the valve to its seat even as carbon builds up. It is determined by valve contact area and valve seating characteristics. Nose force is required to control the motion o...
by David Redszus
Thu Jan 21, 2021 12:14 am
Forum: Engine Tech
Topic: effects of gear and tire diameter change.
Replies: 40
Views: 1104

Re: effects of gear and tire diameter change.

In a drag race application, the most important parameter is linear acceleration. A recording accelerometer (via GPS or sensor) will provide much more useful information than time slips or ass based accelerometers. These can be had for about $450, which is very cheap. If we know the acceleration G fo...
by David Redszus
Tue Jan 19, 2021 11:51 pm
Forum: Engine Tech
Topic: effects of gear and tire diameter change.
Replies: 40
Views: 1104

Re: effects of gear and tire diameter change.

Two simple questions if you please.

Where are the torque curves for your various engine configurations?

Why, in a drag race, the pursuit of speed instead of acceleration G forces?
by David Redszus
Tue Jan 19, 2021 5:58 pm
Forum: Engine Tech
Topic: effects of gear and tire diameter change.
Replies: 40
Views: 1104

Re: effects of gear and tire diameter change.

Considering only rear end and tire diameter:

3.73..26"....20.74 mph/1000rpm
3.73..29"....23.13
4.10..26"....18.82
4.10..29"....20.99
4.56..26"....16.96
4.56..29....18.92
by David Redszus
Tue Jan 19, 2021 12:53 am
Forum: Engine Tech
Topic: Ignition , combustion statement
Replies: 14
Views: 1019

Re: Ignition , combustion statement

sorry to correct , but they don not need the chamber to be rich to have the plug at stoich , in fact they are able to have the total outter section in near full exhaust gasses with the used or egr , which includes running it through the vvt , so in the case of mitsubishi , where the total ratio is ...
by David Redszus
Fri Jan 15, 2021 6:30 pm
Forum: Engine Tech
Topic: polishing a crank
Replies: 16
Views: 1062

Re: polishing a crank

Don't overthink the 'shade tree' method, or try to convince yourself there's any kind of 'science' to it ..... JMO While "overthinking" can be wasteful, "underthinking" can be harmful. As stated above ...... strop it back and forth with a level of sympathy ....... The science is always there, wheth...
by David Redszus
Fri Jan 15, 2021 11:34 am
Forum: Engine Tech
Topic: polishing a crank
Replies: 16
Views: 1062

Re: polishing a crank

Don't overthink the 'shade tree' method, or try to convince yourself there's any kind of 'science' to it ..... JMO While "overthinking" can be wasteful, "underthinking" can be harmful. The science is always there, whether we know it or not. With all the modern metal machining technology available, ...