BEAMS 3S build up... not NA

[The Real Roadrunner]

im starting to think that i should take this thing back and wait for a manual engine to show up instead.

any info on what the Ti valves are like with alot of heat and boost?
i would hazard a guess that the springs wont like boost much so i would have to upgrade them,
this inturn may fatigue them more due to the higher seat pressures placed on them.

is the rumour true that Ti valves will start flaking with high amounts of heat?

cheers
linden

[oldcorollas]

Glenn, did the auto have a different redline? i just can't think of any reason as to why they went for steel valves instead of the titanium ones fitted to a manual, also do they run a different cam profile?

i was just commenting on this... talking about stock setup.. not modded... for modded, use whatever will survive, and then add lightness if wallet allows..

[whatthe?]

Linden's expectations/requirements > stock anything in most cases

[dave368]

i would hazard a guess that the springs wont like boost much so i would have to upgrade them,
this inturn may fatigue them more due to the higher seat pressures placed on them.

From memory, the spring pressures on the stock springs are something like 22 pounds. You'll need to be upgrading them for just about any boost levels

[Celica RA45]

linden you will need to check them at 39.4 which is seated pressure i used the fwd springs which are the same with a 435 thou lift cam and 262 duration for 3 years with no problem
also on the ti valves they have a life alright for std motor but i would be a bit worried of the exhaust dropping heads with 2 much heat
stick with the steel valves and the 31 mm bucket is good for up to 510 thou no problems
i also can get a better valve spring in the 50 lb seated pressure if you are after a set not cheap come from germany 600 a set in our money

[Mos]

Its affect is next to nill. At 10 degrees ATDC (around the time when most pressure is present on piston on power stroke) the difference in your piston heights with a substantially longer rod would definantly be no more then .000015mm, in a short stroke motor like the 3sgte anyhow. Seems unbeleivable?

Unbelievable - 0.0111mm

Mock up an engine with two different rod lengths and test it for yourself. Now tell me how much longer the piston dwells at TDC? heaps isnt it

Why mock it up? Simple trig does the trick...



If anyone finds errors, please lemme know.

Mos.

[oldcorollas]

nup, i got same... but i arranged calc so it was working out distance from TDC.. same result tho
been a while since i bothered with trig

=(43+$B$4)-43*COS(RADIANS(A8))-SQRT((($B$4)^2)-(43*SIN(RADIANS(A8)))^2)

where 43 = half stroke, A8 = column with angle after TDC in degrees, and $b$4 = rod length in mm

if you go to a 160mm rod, the maximum difference is 0.984mm (at 90 deg) instead of 0.394mm

[o_man_ra23]

Onto the Auto/Steel Manual/Ti bit. As mentioned that the Auto is likely programmed to shift below redline.

These motors were destined for luxury sportscars, and were made with the high standards they were in the intent that people wouldn't do cheapo mods like boganise the boxes. They must have expected also that people with the intent of doing anything more than picking the kids up from school would purchase a manual version, thus making the motors more floggable (technical term).

I am reading with interest the technical parts of this, as I intend to do something similar to the RA28 sometime down the track when I have more coin to throw around. I just hope nobody decides to put on sequential turbos in the meantime (take the uniqueness factor out of my intentions)

Also with the rod length... theory would suggest that by having the piston slower at the top of the stroke and quicker at the bottom (by lengthening the rod) this increases the time for the first part of the burn (highest intensity) to push on the piston, thus increasing torque. But as already mentioned, the difference is marginal at best. If somebody would like to work out times in percentage of cycle time, that would be interesting (both would end up at 50% of cycle time at BDC)

[Celica RA45]

now mos what would happen if you did a few changes like a 45mm big end instead of a 48mm bigend that would change the rate to 149mm

[o_man_ra23]

No, as you are working off bearing centre to pin centre. If you offset ground to 45mm there would be a difference.

[oldcorollas]

here is the difference in distance from TDC, for 138 vs 146 and 138 vs 160mm rods...

angle is degrees after TDC, scale on left is the difference in piston position between stock and longer rod... longer rod is closer to TDC

edit: updated with 149mm rod also

bear in mind that a 1mm difference is 2.3% of the stroke up to 90deg...

[Celica RA45]

no just machine big end down to 45 mm no off set at all then make rod another 3mm longer from 146to 147.5 most likely

[The Real Roadrunner]

no just machine big end down to 45 mm no off set at all then make rod another 3mm longer from 146to 147.5 most likely

your not changing where the bigend centreline is so the only way to get a longer rod is move the piston pin hieght.

if you offset ground the crank to reduce the stroke then your theory would be correct and you can run a longer rod.

cheers
linden.

[jeffro ra28]

Well mos has cleared up ALL of my my inaccurate ballparks anyhow (thanks for going to the effort mos). However its still SFA in the scheme of increasing performance by way of "increasing dwell at TDC". Unless ofcourse you can increase rod lengths by 15mm odd.

[The Real Roadrunner]

However its still SFA in the scheme of increasing performance by way of "increasing dwell at TDC". Unless ofcourse you can increase rod lengths by 15mm odd.

while i do believe there isn't much of a difference, there still is one and if you calc the 8000rpm rotations down to milliseconds the piston does still stay at TDC for longer and travels lower down the bore therefore proding more torque.

measureable? probly a single KW (stab in the dark) at say 6000rpm but it would still allow you to rev the engine harder for the same given peak piston speed thus giving more KWs as the revs rise above this point : ie torque drops off massively after 8300rpm but fit an 8mm longer rod it may allow you to rev to 8800rpm?

as stated im just a fabricator and no maths genius but i have the ability to think about things in "outside the box" ways.

im going to do a leakage test on the engine tomorrow to find out 100% whats going on with this thing and base my decisions off my findings,
i still cant bring myself to rebuild it with an 86mm stroke though as i don't need to rev the tits off a turbo motor to get the required power and believe that cubes will make up for any lack of revs this may cause.

too many thoughts make my head hurt.

cheers
linden