What to make the 3sgte compression ratio?

[RedMist]

Its a hard question to answer. I just wondered what compression ratio I should be heading for with my 98 Octane 3SGTE.
The engine is fresh, Wiseco Pistons, stock cams, won't be running a tonne of boost as I dont know how much I can push through the 36mm rally restrictor. It will also be running antilag which may push chamber temps up.

[vvega]

10:1
but you want a good ecu and a even better tuner

[fivebob]

Depends on how much boost, and how you plan on varying the compression ratio. The restictor shouldn't be a problem if you have freedom to place it where you like (i.e. as far away from the turbo inlet as possible)

IMHO thicker headgaskets are a bad idea as the promote detonation by reducing the effectiveness of the squish area, so I'd stick with the whatever CR you have when fitting a stock H/G (or even a thinner one ) which IIRC is about 9:1. Careful tuning using Minimum Advance for Best Torque principles should be safe.

Water injection would allow you to run a bit more compression

[strx7]

i'm running 9.5:1 on my 5S cranked, 3SGTE with 264 degree cams.

[RedMist]

Depends on how much boost, and how you plan on varying the compression ratio. The restictor shouldn't be a problem if you have freedom to place it where you like (i.e. as far away from the turbo inlet as possible)

IMHO thicker headgaskets are a bad idea as the promote detonation by reducing the effectiveness of the squish area, so I'd stick with the whatever CR you have when fitting a stock H/G (or even a thinner one ) which IIRC is about 9:1. Careful tuning using Minimum Advance for Best Torque principles should be safe.

Water injection would allow you to run a bit more compression

The restrictor has to sit bolted to the compressor housing and the restriction must be no further than 50mm upstream of the blades. So its most certainly going to create issues in terms of volume of air.

My only real option was to increase compression ratios. I dont like thicker head gaskets or removing squish bands. The Wisecos are already here so I cant alter the dome. So it was either plane the head or install my TRD head gasket. Wiseco rate the pistons at 9.0:1 CR probably due to the larger bore size (86.5mm).

I have two new headgaskets, one stock Toyota and the second a TRD. I have no preference as to which I use.

I possibly presented the question incorrectly. If I'm aiming for a 300hp enigne what should my CR be given the following.

Cams will also be replaced when I have the cash so speccing them now should be advisable. A very short duration, high lift intake cam, and a very long duration exhaust cam.
Antilag (Group N augmented by throttle bypass. )
Water Injection (ST205)
Stock WTA with spray bar
Cold air intake
Wiscos
Eagle Rods
ACL bearings
LEM3, IAT boost adjust.
LC1 wideband.

Knock probably wont work depending on how much noise it picks up from the solid engine mounts and underbody protection.

My thinking was, because of the flow restrictions I would want a reasonably high CR around 9.5 to one. However I know nothing about restrictors or hair dryers. Lowest CR I've ever run was 12.5:1.

[RedMist]

i'm running 9.5:1 on my 5S cranked, 3SGTE with 264 degree cams.

Your dynamic compression will be considerably lower than mine given the duration of your cams.

[fivebob]

i'm running 9.5:1 on my 5S cranked, 3SGTE with 264 degree cams.

Your dynamic compression will be considerably lower than mine given the duration of your cams.

That depends entirely on the volumetric efficiency of the engine, it may well be higher at certain certain points in the boost/rpm curve.

[strx7]

i was wanting something that wasn't too slugish off boost, the 91mm stroke should help my cause and I believe it should get a pretty wide power band. I'll know in 6 weeks hopefully as that is D Day

[fivebob]

The restrictor has to sit bolted to the compressor housing and the restriction must be no further than 50mm upstream of the blades. So its most certainly going to create issues in terms of volume of air.

Bastards All the info I have suggests that retrictor flow can be increased if it's place well before the turbo. At 50mm you'd have problems with getting enough taper after the restrictor to match the turbo inlet without causing flow problems. Is the shape of the restrictor fixed, or does it just have to be 36mm at it's narrowest point?

My only real option was to increase compression ratios. I dont like thicker head gaskets or removing squish bands. The Wisecos are already here so I cant alter the dome. So it was either plane the head or install my TRD head gasket. Wiseco rate the pistons at 9.0:1 CR probably due to the larger bore size (86.5mm).

I have two new headgaskets, one stock Toyota and the second a TRD. I have no preference as to which I use.

In that case use the thinnest one, and that will help the squish area do it's job.

I possibly presented the question incorrectly. If I'm aiming for a 300hp enigne what should my CR be given the following.

Is that 300HP at the wheels?

If so, then you'll need a better turbo than the CT20B. Which in a 4WD would be pushed to get more than 280-290HP. Best I've seen is around 310rwhp on a MR2. Given the 4wd, and the fact that the compressor will be operating at reduced efficiency and therefore heating the intake charge more, then I think you'd be lucky to see 275whp

Cams will also be replaced when I have the cash so speccing them now should be advisable. A very short duration, high lift intake cam, and a very long duration exhaust cam.

I wouldn't recommend this strategy, 264's have been proven to give the best overall power characteristics on 3S-GTEs. see http://www.cj-motorsports.com/camtest.htm for graphs of all the combinations.

Antilag (Group N augmented by throttle bypass. )
Water Injection (ST205)
Stock WTA with spray bar
Cold air intake
Wiscos
Eagle Rods
ACL bearings
LEM3, IAT boost adjust.
LC1 wideband.

Knock probably wont work depending on how much noise it picks up from the solid engine mounts and underbody protection.

Knock will still work, but it's not that good anyway. Best idea is to tune on a load type dyno like a Dynapack using Minimum Advance for Best Torque, and not worry about knock detection.

My thinking was, because of the flow restrictions I would want a reasonably high CR around 9.5 to one. However I know nothing about restrictors or hair dryers. Lowest CR I've ever run was 12.5:1.

9.5:1 should be OK with water injection, even 10:1 should be possible if your tuner is very good. But I would be tempted to invest in a bore scope and check the condition of the pistons after running it for a while just to make sure you aren't getting too much detonation

[RedMist]

Bastards All the info I have suggests that retrictor flow can be increased if it's place well before the turbo.

As do I. Unfortunately its quite clearly defined in Schedule A of the NZ motorsport manual PG 34 has a picture.
http://www.motorsport.org.nz/Pdf/M33%20App2%20SchA.pdf

At 50mm you'd have problems with getting enough taper after the restrictor to match the turbo inlet without causing flow problems. Is the shape of the restrictor fixed, or does it just have to be 36mm at it's narrowest point?

Its certainly going to pose issues for a turbo like the CT20b. Shape is open, but we have completed some basic flow tests and the optimal shape at the moment seems to be a bellmouth on entry to the restrictor. It appears a ramp (as pictured in pg 34) attempts to force all air more centrally after the restriction. So we are currently spinning up a bellmouth onto the 36mm restriction then a flare out onto the compressor housing of the CT20b.

I possibly presented the question incorrectly. If I'm aiming for a 300hp enigne what should my CR be given the followingIs that 300HP at the wheels?

If so, then you'll need a better turbo than the CT20B. Which in a 4WD would be pushed to get more than 280-290HP. Best I've seen is around 310rwhp on a MR2. Given the 4wd, and the fact that the compressor will be operating at reduced efficiency and therefore heating the intake charge more, then I think you'd be lucky to see 275whp

I've just rebuilt the CT20b so wasn't planning on straying far from this path for the first season or so. I was hoping for 300whp as I know I'm running a weight deficit to the Evo 3's (also in pre 96) 275whp about where most of the pre 96's are running. It just means I'm going to have to be a little more on the edge than I expected.

Cams will also be replaced when I have the cash so speccing them now should be advisable. A very short duration, high lift intake cam, and a very long duration exhaust cam.

I wouldn't recommend this strategy, 264's have been proven to give the best overall power characteristics on 3S-GTEs. see http://www.cj-motorsports.com/camtest.htm for graphs of all the combinations.

The cams arent to attempt and get more power, although they may be useful to shift as much torque down the curve as possible. They are a simple method to 1. work around the intake restrictions. 2 get as much exhaust flow as possible for a quick spool.

Borescope... good idea.
http://cgi.ebay.com/PROVISION-100-BORE- ... dZViewItem

That do?

With CR: I think I'll stick conservative and go 9.5:1

[soopachargen]

probably not much help... but will making the restrictor venturi shaped (is that how if should be said) increase airflow through the restrictor??

[fivebob]

At 50mm you'd have problems with getting enough taper after the restrictor to match the turbo inlet without causing flow problems. Is the shape of the restrictor fixed, or does it just have to be 36mm at it's narrowest point?

Its certainly going to pose issues for a turbo like the CT20b. Shape is open, but we have completed some basic flow tests and the optimal shape at the moment seems to be a bellmouth on entry to the restrictor. It appears a ramp (as pictured in pg 34) attempts to force all air more centrally after the restriction. So we are currently spinning up a bellmouth onto the 36mm restriction then a flare out onto the compressor housing of the CT20b.

Be careful that you don't have too steep a taper after the throat, as that will cause the airflow to detach, create turbulence and reduce flow. If a straight taper is much more than about 8° then I would suggest making it a bellmouth on exit from the throat. IME what happens after the throat is as important as what happens before. Also a radius before and after the parallel section of the throat will help keep the flow attached.

I wouldn't recommend this strategy, 264's have been proven to give the best overall power characteristics on 3S-GTEs. see http://www.cj-motorsports.com/camtest.htm for graphs of all the combinations.

The cams arent to attempt and get more power, although they may be useful to shift as much torque down the curve as possible. They are a simple method to 1. work around the intake restrictions. 2 get as much exhaust flow as possible for a quick spool.

If you look at the page I linked to you will see that 264° intake/exhaust produces better power down low than 264°/272°. Extra duration on the exhaust wont give you quicker spool and it's quite possible that it will give a slower one. You can get a faster spool by retarding the ignition timing, but that is at the expense of power off boost.

Borescope... good idea.
http://cgi.ebay.com/PROVISION-100-BORE- ... dZViewItem

That do?

Should be ok, but I have had no exerience with that particular brand.

With CR: I think I'll stick conservative and go 9.5:1

Good Idea

[Mr Revhead]

dont stress too much about 20 odd hp in a rally car....


work on your driving

[vvega]

my thoughts woudl have been that the increased overlap woudl help prevent det thought the midrange
that extra wsted charge helps keep everthign cooled down

my current in the build is a beams motor and i plan to use the vvti to give me that overlap thougth any det problems whilst still been ablle to minimise overlap at higher rpm
in"my" theroy it shoudl offer a wider rance of controled dynamic compression

im only looking for 450 hp but i want the fattest curve under peak power can
as it is with anothonym's custom gt3071 i get a solid 1 bar well before 3 grand and it has no trailing off at this stage before teh 8 grand redline ive set...though i must say my current i/c setup only allows a few foot down runs before temps start getting above 50 degrees

im hopping with the new 10:1 motor ill have earlier spool and way more "Drive" than the excessive amout i already have

can you run a later modle head redmist?? perhps a beams jobbie ?

[RedMist]

dont stress too much about 20 odd hp in a rally car....


work on your driving

THATS the last time I let you come to watch me walk out of a forest.

[RedMist]

can you run a later modle head redmist?? perhps a beams jobbie ?

I could. However I've just spent a good deal of money getting my current gen 3 head worked.

[Mr Revhead]

i wasnt referring to that!

with rallying, as you probably know, the driver plays such a huge part that 20hp can be overcome..... by some!
so...... you the next possum?

[vvega]

oh look two moons

[RedMist]

Be careful that you don't have too steep a taper after the throat, as that will cause the airflow to detach, create turbulence and reduce flow. If a straight taper is much more than about 8° then I would suggest making it a bellmouth on exit from the throat. IME what happens after the throat is as important as what happens before. Also a radius before and after the parallel section of the throat will help keep the flow attached.

I no longer have the CT20b here as the restrictor is being spun-up and mounted. But your saying if I cant achieve an 8 degree ramp I should simply plate off the intake at 50mm from the blades, cut a hole in it and bellmouth the opening to 36mm? We have already done flow tests using an entry ramp and it just doesnt aid flow. So no ramps either side? I'm going to have to flow test this one.

[fivebob]

Be careful that you don't have too steep a taper after the throat, as that will cause the airflow to detach, create turbulence and reduce flow. If a straight taper is much more than about 8° then I would suggest making it a bellmouth on exit from the throat. IME what happens after the throat is as important as what happens before. Also a radius before and after the parallel section of the throat will help keep the flow attached.

I no longer have the CT20b here as the restrictor is being spun-up and mounted. But your saying if I cant achieve an 8 degree ramp I should simply plate off the intake at 50mm from the blades, cut a hole in it and bellmouth the opening to 36mm? We have already done flow tests using an entry ramp and it just doesnt aid flow. So no ramps either side? I'm going to have to flow test this one.

No, what I'm saying in the you need to bellmouth the entry and exit if the exit taper is greater than 8°.

I see if I can find time to take some measurements from the CT20B and draw it up.