Update on 3.2ltr 16v turbo race car.

[333pg333]

[333pg333]

Just in case any of you are having trouble sleeping...

I punched in all the specs from the original motor to Ai and advised it that we're moving from 94mm to 88mm stroke while using the original pistons. It advised us to order rods with 155mm ccl. That would lower the c/r from 8:78.1 to 8:29.1 which isn't ideal. But not insurmountable with tuning and a little extra boost.

I then asked it what c/r it would suggest running race fuel E85 and max boost of circa 22psi. It suggests 10:5.1 is the sweet spot and that's with some reliability built in. I remember when I specc'd the original motor with the og builder he wanted to go higher than the 8:8.1 that we wound up with. I was being somewhat conservative back then. I wonder if I should consider ordering new pistons too? Could go for 9:5.1 - 10.1 to be extra safe. I don't want to increase peak cylinder pressure too much. Thoughts?

[Tom]

Just in case any of you are having trouble sleeping...

I punched in all the specs from the original motor to Ai and advised it that we're moving from 94mm to 88mm stroke while using the original pistons. It advised us to order rods with 155mm ccl. That would lower the c/r from 8:78.1 to 8:29.1 which isn't ideal. But not insurmountable with tuning and a little extra boost.

I then asked it what c/r it would suggest running race fuel E85 and max boost of circa 22psi. It suggests 10:5.1 is the sweet spot and that's with some reliability built in. I remember when I specc'd the original motor with the og builder he wanted to go higher than the 8:8.1 that we wound up with. I was being somewhat conservative back then. I wonder if I should consider ordering new pistons too? Could go for 10.1 to be extra safe. Thoughts?

What's the bore? I have a 104mm x 88mm 3 liter at maybe 9.5:1 compression and have struggled with knock even when I was using e85. What head will you use? Mine is an 8v with slightly larger intake valves and very mild porting. I guess the 16v head could change the equation, but otherwise I think your AI pal is crazy. You can always turn up the boost but you can't turn down the compression. Just my 2 cents.

[333pg333]

Original build specs here Tom. I don't think 9:5.1 should be too high with this head. 374cfm @ .550 lift / 28". That's significantly higher than even a big 8v.


Engine 4 Cyl in line 4
Engine displacement 3240.30cc
Bore 104.75mm
Stroke 94.00mm
Max RPM 8800 RPM

Block Closed Deck
Deck Ht 229.997mm
Girdle Fully doweled

Crankshaft stock offset ground for added stroke
Stroke 94.00mm
Main journal dia 70.00mm
Rod journal dia 48.00mm

Connecting Rod Carrillo H Beam
BE bore 51.00mm
SE bore 21.00mm
CCL 152.00mm
Bolts 3/8” Carr

Piston CP Forged X102
Piston gauge dia 104.673mm
Comp Ht 30.886mm



Cylinder Head 968 ported
Valves 4/Cyl
Chamber vol 37.20cc
CR 8.78:1.0
Intake Valve dia 41.00mm
Exhaust valve dia 35.0mm
Gasket 5 layer Cometic
Sealing Garlock
Torque
1st stage 20 ft/lbs in factory seq wait 15 mins
2nd stage in reverse order loosen + 25ft/lbs wait 15 mins
3rd stage 90° wait 30 mins
4th stage 110°
Intake Camshaft
Seat duration 285° @ 0.014”
0.050” duration 253.5°
Gross lift 0.502”
Hot lash 0.014”
Net Valve lift 0.488”
Cold lash 0.011”
CL 114° ATDC
Final assy 114.50°
Exhaust Camshaft
Seat duration 276° @ 0.014”
0.050” duration 235.6°
Gross lift 0.443”
Hot lash 0.014”
Net Valve lift 0.429”
Cold lash 0.011”

[Bergerac]

I'm running 9.1:1 on 98, 9.5 on E85 doesn't sound extreme

[944crazy]

Original build specs here Tom. I don't think 9:5.1 should be too high with this head. 374cfm @ .550 lift / 28". That's significantly higher than even a big 8v.

Crankshaft stock offset ground for added stroke
Stroke 94.00mm
Main journal dia 70.00mm
Rod journal dia 48.00mm

Connecting Rod Carrillo H Beam
BE bore 51.00mm
SE bore 21.00mm
CCL 152.00mm
Bolts 3/8” Carr

Going off the specs above, the pin height from crank centreline on your pistons is (94mm/2) + 152mm = 199mm

Factory specs are (88mm/2) + 150mm = 194mm. So your pistons have a pin height that is 5mm further from the crank centreline. To compensate you would indeed need 155mm CCL length rods, so AI was right on the money there. Not sure about that 10.5:1 comp ratio though

The slightly longer rods do give a slightly more favorable rod to stroke ratio. Looks like there are LS v8 rods around with a 6.125 inch CCL which is very close the 155mm you need, so Carillo should at least have the correct sized forgings on hand.

[Bergerac]

Going to need a seperate Aussie 3L chat if we keep going at this rate

[333pg333]

Haha....all are welcome.

As far as c/r goes, of course we're seeing much higher ratios than we're used to dealing with re our motors. In the past I've somewhat rejected higher c/r as the cars that I've driven with high c/r and forced induction were too linear. Street cars of course. They were boring. So I was happy with a bit of lag and then the irresistible punch in the back. But of course this is not the fastest way around the track. I think we can find a happy medium. Parking all this for one moment...the idea is to put this car back together and then sell it. So perhaps spending more is just a bit silly. Spending & More should be the name of my solicitors...

[Thom]

IIRC Duke started with a CR of 9.x:1 then gradually took it down to 8:1 along with fitting ever more aggressive camshafts, ending up with the torque "curve" of a supercharged engine - an almost straight diagonal line peaking at peak rpm.
I wouldn't consider anything higher than 9:1. As Tom said it is far easier to turn up the boost on a large turbo that will be more efficient with lots of boost and adjust the timing profile accordingly than being cornered with a high CR and little to no headroom. It's a race engine that needs to deliver between 5 and 8k rpm, who cares if it's a bit sluggish down low, which it even won't in a lightened race car.
Just my 0.02€.

[Tom]

I'm running 9.1:1 on 98, 9.5 on E85 doesn't sound extreme

16 valve head?