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Search found 3777 matches

by David Redszus
Wed Feb 01, 2023 11:16 am
Forum: Chassis / Suspension / Body
Topic: Shaving/buffing tyres for endurance racing?
Replies: 5
Views: 138

Re: Shaving/buffing tyres for endurance racing?

Almost all (95%) of the tire grip comes from two parameters: vertical loading and slip angle. All the rest; camber, compound, temp, pressure, etc., comprise the remaining 5%. Vertical loading is determined by a combination of static corner weights and dynamic weight transfer. The best result occur w...
by David Redszus
Tue Jan 31, 2023 5:35 pm
Forum: Engine Tech
Topic: Alternative fuel enrichment
Replies: 29
Views: 917

Re: Alternative fuel enrichment

The question regarding fuel enrichment when selecting alternate fuels is not easily answered from simple inspection of presented data. Before we examine the proceedure, let's look some fuel basics. In order to burn, the engine needs both air and fuel. The fuel must be in a vapor form, not a liquid. ...
by David Redszus
Sat Jan 28, 2023 6:53 pm
Forum: Engine Tech
Topic: Selecting a compression ratio
Replies: 27
Views: 1196

Re: Selecting a compression ratio

Well, if nothing else it points out that that particular engine doesn't like a DCR that high. At least that's a conclusion I might draw from that example. DCR is not a stand alone metric to predict octane requirements. DCR must be used in conjunction with inlet air pressure and inlet air temperatur...
by David Redszus
Sat Jan 28, 2023 6:43 pm
Forum: Engine Tech
Topic: Alternative fuel enrichment
Replies: 29
Views: 917

Alternative fuel enrichment

As is often the case, an engine built for certain fuel blend must be run on some other blend, either due to dyno issues, track regulations, or availability. Now the problem becomes to determine which alternative fuel will perform similar to our original fuel and is a change in enrichment necessary? ...
by David Redszus
Sat Jan 28, 2023 12:28 am
Forum: Engine Tech
Topic: Selecting a compression ratio
Replies: 27
Views: 1196

Re: Selecting a compression ratio

Even with all my errors, which of you already posted that DCR results may vary widely? [crickets] Good point. As you said; crickets. But it was not the DCR that varied widely. It was the fact that the engines were not the same. But who knew that DCR, by itself has limited value; its only a ratio an...
by David Redszus
Fri Jan 27, 2023 11:06 pm
Forum: Engine Tech
Topic: Selecting a compression ratio
Replies: 27
Views: 1196

Re: Selecting a compression ratio

DCR is not as valuable as commonly believed. Actually, DCR may be even more valuable than commonly believed. SBC 350 V8, 3.48" stroke, 5.7" rod, same chamber, same spark (using as 1.25 ratio of variable heats) In order to produce the SCR and DCR values listed below, the two engines cannot have the ...
by David Redszus
Fri Jan 27, 2023 12:31 pm
Forum: Engine Tech
Topic: Selecting a compression ratio
Replies: 27
Views: 1196

Re: Selecting a compression ratio

If I was designing a performance engine off of dcr formulas ,my dcr would be higher than allot of guys static number they think to be safe. Perhaps the problem is a lack of understanding of DCR and its function and usage. DCR can never be higher than SCR; but it is still just a ratio of volumes. DC...
by David Redszus
Thu Jan 26, 2023 11:56 am
Forum: Engine Tech
Topic: Head Porting for Fuel Milage
Replies: 53
Views: 1549

Re: Head Porting for Fuel Milage

Raise the compression ratio. That will improve efficiency across the entire rpm range.

Put it on a dyno and plot the BSFC curves.

Drive the vehicle in the rpm sweet spot. (see typical BSFC curves)
by David Redszus
Wed Jan 25, 2023 11:27 am
Forum: Engine Tech
Topic: Clover Lapping Compound
Replies: 32
Views: 907

Re: Clover Lapping Compound

If we were to use a surface profilometer to obtain the Ra of both valve and seat, we would quickly understand that we are attempting to mate two minature mountain ranges. Lapping with a fine compound will reduce the peaks but not eliminate them. When the engine is fired and run for a while, those se...
by David Redszus
Wed Jan 25, 2023 11:07 am
Forum: Engine Tech
Topic: lapping valves and seats necessary?
Replies: 42
Views: 2493

Re: lapping valves and seats necessary?

I wonder what a strip of Plastigage, laid perpendicular cross the seat with the valve pressed in place,
would look like. It might provide a visual of seat width and seat angles.
by David Redszus
Mon Jan 23, 2023 7:39 pm
Forum: Engine Tech
Topic: Mating Two V8's, ( Freight Train) vs. Harmonics
Replies: 26
Views: 1127

Re: Mating Two V8's, ( Freight Train) vs. Harmonics

All I remember is what I was told fifty years ago from a guy who raced something similar. He said, 45-degrees seems like it should be the way to go, but keeping them in line at 90-degrees is what actually works best. Fifty years ago, Porsche linked two 911 engines in series to create the 917. Beat ...
by David Redszus
Mon Jan 23, 2023 7:34 pm
Forum: Engine Tech
Topic: Question about boost.
Replies: 21
Views: 700

Re: Question about boost.

Let's build a paper engine to compare the effects of turbocharging. B = 89.15mm S = 80.0mm R = 135mm Disp = 2.0L NA engine SCR = 12.0 DCR = 9.39 BMEP = 11.03bar Power = 223hp @ 9000rpm (mSp = 24.0 m/s) Turbo engine SCR = 9.39 Boost = 14.3 psi BMEP = 21.75bar Power = 223hp @ 4550rpm (mSp = 12.1 m/s) ...
by David Redszus
Thu Jan 19, 2023 8:49 pm
Forum: Engine Tech
Topic: Gearing Down for Altitude: Dyno Results?
Replies: 10
Views: 415

Re: Gearing Down for Altitude: Dyno Results?

panic wrote: Thu Jan 19, 2023 11:54 am As air density goes down, heat removal by convection is reduced.
Don't lean it out too much.
Yes, but so is the heat produced by the engine.

Get out the old O2 sensor. :)
by David Redszus
Thu Jan 19, 2023 12:48 am
Forum: Engine Tech
Topic: Gearing Down for Altitude: Dyno Results?
Replies: 10
Views: 415

Re: Gearing Down for Altitude: Dyno Results?

I'm considering purchasing a house in Mexico City in addition to my place in New York City. I ride only air cooled, carbed, single cylinder motorcycles, they're my favorite and that will never change; as such, I'll be taking a favorite moto from NYC to CDMX with me.  But here's the issue: While NYC...
by David Redszus
Fri Jan 13, 2023 4:15 pm
Forum: Engine Tech
Topic: Valve Seat Cut Width Measurement
Replies: 14
Views: 603

Re: Valve Seat Cut Width Measurement

Seems to me that we have two issues: How wide is the seat? How wide should it be? While the seat widths should be similar for consistency, the wrong seat width will affect heat transfer from the valve to the seat. BMW engine specs: intake 0.09 x VHD, exhaust 0.115 x VHD. Each specific engine should ...