Old Splatterhand

keep this thread going

btw: is "Bridgeport" written on that mill? hehe



do you guys use any sealant for the pport so water can't brake thru?

like jb weld or something? or is the tight fitting alum. sleeve enough?

kahren

you are supposed to use devcon aluminum putty around in that water jacket area there.

or whatever other putty you may like more

Lynn E. Hanover

The 13B will tolerate more advance that my 12As but over 30 is just making hotter water temps.

More like 24 to 28 degrees is plenty up to 9,000 RPM then a dyno to see what works on up. It will even start and idle at 24 degrees. So the ignition can be a fairly simple crank triggered setup.



EGTs at best power around 1575 to 1600. You can go way higher than that and get a bit more but with shorter apex seal life.



That 1587 at 9,000 RPM is an A/F of 13.2. Pertty good tuning.





Lynn E. Hanover

Lynn E. Hanover

Got that "Ifrnaview". I have to make the printing a bit bigger as the conversion seems to hose it up a bit.





Thanks.



Lynn E. Hanover

Lynn E. Hanover

http://home.earthlink.net/~mmc1919/venturi.html





Go to the link above an play with Mr. Bournulli's principal.



Notice that when the tube size is increased, the flow velocity goes down. So the ideal diameter (and length)for any particular RPM, is that which gets the largest volume of mixture into the chamber before the port is closed. Pretty simple.



However, the ideal is not available to most of us. The Lemans engine had veriable length tubes, and they were smaller than you would think. This because there are only 6 speeds in the gearbox to cover parkinglot 90 degree turns, and a three mile straight at 230 MPH. So that engine was not designed for max power.

It was designed to have a wide power band.



So, it had smaller diameter runners to keep flow velocity high, and adjustible length runners to get the wide torque of the (tuned length) runner.



So your car can have 300 HP and another car can have 250 HP and beat the crap out of you. The power available has to have a wide enough "band" to cover the trans ratios you have.



Otherwise, when you look at the dyno sheet and see that a 1200 RPM drop from a shift at 9,000 RPM puts you at 7,800 RPM (actually lower because the car deccelerates quickly during the shift) so , guess 7,700 RPM,

and the dyno sheet says that only 220 HP is available at 7,700. So 300 HP at 9,000 is of no value without the wide power band. So after that particular shift, the car is on its face for a second or so while it gets back up on the pipe (or tune (returns to an RPM where adequate power is available)). So the clown with the home made engine kicks your but again. And he does it down the straightaway where you (with you high doller monster motor should be king).



Starting to see a picture here?



There was an old saw (a saying) that went: HP sells engines. Torque wins races. And now you know that even this is misleading. HP sells engines. A wide power band wins races. Screw the peak power number.



Is it possible to build up a killer bridgeported engine an go slower through the speed range. Have ETs that seem poor in realtion to the money expended. Why sure. People do it every day. If you have a stock gearbox with big steps between gears, the engine may fall off the tune with every shift. That *** hole beat me again and his engine is almost stock. Get the engine builder on the phone.



You must lay the RPM drops between gears on top of the dyno power curve to see where to shift, and to see how far to lead a gear before shifting. So, if best power is at 9,000 and you shift at 9,000 you leave a third of the power on the table. So you see on the dyno sheet that it still has 270 HP at 9,600 RPM. So you subtract the 1200 RPM drop for that gear change an see 8,400 RPM and check the dyno sheet to see that you will be shifting into 240 HP. Add in the additional RPM drop caused by aero drag during the shift, and addition RPM drop for the change from 4th to 5th where the highest aero drag lives. Also, there may be a loss caused by a first or 5th gear that is outside the H gate. So call it 235 HP. Tape the shift RPM for each gear on the dash until you know them.



Now notice that the rear end seems to be getting loose leaving some turns. (Its the additional power upsetting the rears). You finally beat the kid with no money who makes his own engines.



But I run on as usual..............



The highest runner velocity attainable without injuring your peak power, (and even if it hurts a little) will give you an engine that feels good everywhere in the RPM band. Charges off of corners and even if you need to pull it down off the power here or there it snaps right back with little time lost. It also will give you more power lower in the RPM range than you have now.



Take two power curves and lay them out on a big piece of 1/4" graph paper. Draw a line through the curve at some RPM. Which one has the widest power band? Which one has the highest average HP for each RPM.



Slide a yard stick back an forth across each line and see what HP any particular gear drop RPM would leave you at. How far would you overwind do stay in the power for each RPM drop?



Add up the little squares to see which one has the most area under the curve.



There you go. More than you wanted to know about runner size.





Lynn E. Hanover

REZCAR

OK, my pea sized brain understood all that...I just never heard it worded the way you said it. Same for "fall off tune" or "an old saw"!

Owen

Kim

Ha I dont think my boss would appreciate me sending the mill to the states

Though we do have a factory in the states too, it would be possible hmmmm.



Runner ID is 51mm, same as the Weber IDA which we are going to use.

It looks about the same projected area as the fucked up MFR housing the car used to run before i bought it.

http://www.wankelkim.net/rx7/fb/PICT0878.JPG



Kim K. Nielsen

Lynn E. Hanover

That 51MM is plenty until you sort out how much RPM you can stand. That will be enough for 300+ HP in a NA

13B, and well under 10,000 RPM.



That housing looks like the older style with the "D" shaped port. Like early 12A housings. I would leav in that feature too, for the start of the project.



Lynn E. Hanover

Kim

Hehe bump

Lynn E. Hanover

In general terms, failed forks inticate overenthusiastic shift speed.



This is very macho stuff, that fast shifting. So, the faster the shift the bigger your...........................



problems with broken parts. This usually a result of not knowing what goes on inside a transmission. There are people out there who rebuild transmissions every day and have little or no understanding of how they work.



So here we go.....How do they work you ask?



The primary function is to multiply torque. While there is considerable multiplication in the differential, it is not nearly enough to allow starts from zero MPH and a reasonable top speed. Lest we have to have a large diesel engine with whopping huge amounts of torque just off idle. And of course the reverse thingy is usefull from time to time.



In addition to reverse there are a number of reductions garsets and in some transmissions an overdrive garset. One selection in each trans is just connecting the input shaft (the splined one at the front the clutch disc turns) and the output or tailshaft (the one the front driveshaft yoke splines onto.



We are talking about front engined (in line) drivelines here, but the same parts appear in sidewinders and rear transmissioned or engined cars.



Get out a picture of a transmission and follow along.



You let the clutch pedal off the floor with first gear engaged. Torque is applied to the input shaft and it begines to turn in engine direction.

Note that the big gear at the front of the counter shaft (the shorter second shaft below the mainshaft) is always engaged with the input shaft gear no matter what. So, the turning the input shaft, turns the countershaft in the opposite direction to (or counter to) the input shaft direction.



So the whole time the engine is applying power to the transmission that is what it is doing. Turning the countershaft. Up through the gears to top gear in most cases that will be no gear reduction at all, but just connecting the input shaft to the output shaft with no reduction or a ratio of 1:1. That's one to one.



In some cases 4th is one to one and 5th is an overdrive. That means the out put shaft is actually turning very slightly faster than the input shaft (engine RPM).



The good part is that the gears on the mainshaft are always engaged with and are being turned by the gears on the countershaft. This is called constant mesh or a constant mesh transmission. The mainshaft gears ride on bearings and are free to spin along at the ratio determined by their tooth counts. Easy to imagine, yes?



When you select a gear, for example first gear. What happens? There are sleeves located between each two gears on the main shaft. The sleeves (called sliders) are moved by the shift forks. the inside of the sliders are splined onto hubs that are in turn splined onto the mainshaft. The face of each mainshaft gear has a set of short splines that also match the splines inside the slider. The shift fork moves the slider until the slider locks onto the gearface splines. Now that first gear in no long free to spin without doing work. No the torque from the countershaft will appear in the main shaft and the car begines to move.



There is a trick that everyone uses to make fitting those rather fine splines together in a short time period.



The synchronizer. Just inside the spline diameter on each gear is a shiny cone. Each slider pushes along ahead of it a brass or steel synchronizer that has splines engaged by the splines inside of the slider. As the slider is moved onto the gear to be selected the conical surface of the synchronizer runs up onto the cone on the gear just as the splines are to touch. This synchronizer to cone engagement is a small clutch. As it grips the cone, it will spin the whole transmission up in RPM or down in RPM so that there will be zero speed difference between the slider, Driven by the output shaft (ground speed) and the gear being selected, driven by the countershaft (engine speed).



Notice that all of the spline sets on the gears and inside the sliders are pointed. Or at least they were when new. As you can imagine, it is more likely that slipping the two spline sets together if both are pointed instead of them being flat on the ends.



This system works just Dandy so long as the shift is performed slowly enough that the whole transmission can be accellerated by or decellerated by......that little clutch, the synchronizer. On a wide ratio transmission a gear change might mean a 1,700 RPM drop on an upshift. That means that the synchronizer must arrest the speed of the countershaft, input shaft, clutch disc, bearings, oil and even the reverse idler, to zero relative speed, in that 1/4 second it takes to make the shift. You cannot do that on the bench with welding gloves on. In fact you can't even stop the input shaft from 1,700 RPM in 1/4 second.



But that is what you demand of the transmission during each upshift and down shift.



As Big Bob Gearjamer goes through the gears way too fast what is happening you ask?



There is not time for the work to be done by the synchronizer. Work= massXdistanceXtime. So the relative speeds between the splines on the gears and the splines on the inside of the slider have begun to engage at more than zero relative speed. That unhappy feeling in the shift lever even if the shift is completed. You konw you screwed up a little. You're not an idiot.



That bad feeling was the tips of the points on the spline sets touching at some speed above of zero.



Continous abuse results in warn out synchronizers, and then warn out splines in the sliders.



The speed shifer gizmos just make things worse by speeding up the shift.



Once the synchronizer has worn out, the splines will wear away, enough to get through the case hardening and begin to mushroom on the ends. The Richmond Gear trans does this. Then on a shift the damaged splines hang up on the hub, and leave the driver stuck in a single gear.



In my opinion, broken forkes indicate abuse of a transmission punishable by not more than 6 months of confinement at hard labor.



Fortunately, the sliders are a bit softer than the gears. A rebuild with new synchros and sliders will fix just about all of it.



Some help:



Shift slower, particularly if damage is allredy suspected. If grating is still bad even when shifting slowly, skip that gear when possible.



Use a synthetic gear oil designed spcifically for manual transmissions. This helps the synchronizer get a better grip on the cone.



Never put used synchros back into a trans. They are just not that expensive. Put in new. If you hang it on a nail, it will find it's way back into a trans someday.



Not for street, but, you can spend a day grinding off every other spline from inside both sliders and gear faces. This makes that 1/8" window that the opposing spline must hit for engagement into a 1/4" hole that's hard to miss. This one works real good. New synchros. Don't forget.



And did you notice that the clutch disc is part of the transmission mass that must be controlled by the poor little synchronizer? So, a lighter clutch disc would make shifting faster and easier on the synchronizer right?

Right again.



There you go. More about transmissions than you wanted to hear.





Lynn E. Hanover