2.8 Short Stroke Compression Ratio fine-tuning

[YTNUKLR]

Just arrived from EBS!

Should be about 10.8:1... I'll start a new thread on this engine soon!!

[Cupcar]

Anyone been using the latest GT3 oil pump in their engines? This is the pump with 2 scavenge pumps.

[Henry Schmidt]

We have used a few and they make huge oil pressure.
In fact maybe too much pressure for some applications.
The two stage scavenge is a nice benefit.

Scott:
One thought on the piston. If you radius the sharp edges on the material between the two valve pockets you will find free horse power.
We have found in excess of 5-7 hp by paying attention to this simple detail.

This is a real performance upgrade, unlike the boat tail myth.

[Cupcar]

Interesting on the piston modification, must improve the crossflow beteween intake and exhaust during valve overlap.

Curious, do you mean the pump makes more pressure than the pressure relief valve can control?

I like the large scavenge pump and want to use with a breather one way valve from a GT3 to try to develop negative crankcase pressure. I wonder if this will create leaks at the early small diameter crankshaft flywheel seal like it did in the GT3

[Steve@Rennsport]

I think the GT-3 oil pumps can put the engine-mounted oil cooler at risk but if thats replaced with the oil filter console (993), you'll not have any problems.

Now,..using the one-way valve from the GT-3 Cup cars might give you some oil leaks,...

[Brother]

Henry, is that engine an MFI 3.0(SC) with slide valve induction and your twin plug set-up? That thing belongs in a centerfold. What kind of power?

[beepbeep]

I was thinking about another thing: wouldn't a very hi-revving engine get away with using slightly higher C/R than low-revving one as VE (thus cylinder filling) would be less perfect on the top?

With other words, engine running VE of 90% on the top would survive with 10% more compression, to do the best possible of available mixture at high revs? You could wind back the ignition where VE peaks upwards 100% and thus save it from knocking but still pull the most of it onn the top?

Just a thought...

[Cupcar]

Now,..using the one-way valve from the GT-3 Cup cars might give you some oil leaks,...

Any ideas why the leaks occurr? The one RMS leak on a GT3 a friend had was minor and appeared to occurr after the engine shut down. This make me think that the RMS must only leak when the oil pressure behind the seal drops. The later RMS seals have the area behind the seal filled to correct the problem.

This makes me think the residual negative pressure in the crankcase after shut down sucks the seal away from the crank and oil in the galleries above is allowed to "burp" out in small quantities as the pressures equilbrate themselves.

I wonder if the large diameter seal is more susceptable to this, than the early seal only one way to find out is to try it myself if nobody else has.

[Henry Schmidt]

Originally posted by Brother
Henry, is that engine an MFI 3.0(SC) with slide valve induction and your twin plug set-up? That thing belongs in a centerfold. What kind of power?

Hi
I am not certain which engine you are asking about.

If you are talking about this engine:
RSR 3.0 case (new) Special machine work to use 3.3 heads and SC cylinders
shuffle pins
95 mm Cosworth pistons 9.8:1
RSR sprint cams
Aasco valve springs and ty retainers
Supertec head studs
Turbo heads,40 mm intake ports
2.2 S crank (66mm)
Carrillo rods
930 oil pump
Old stock after market distributor (Dick Evelrude ?)
1 of 3 custom build slide valve w/custom Supertec pump
Supertec fuel injector lines
Getty Design amber shroud
935 8 pin CDs
Taylor plug wires
European Racing headers w/sport muffler
8500 RPM red line
300+ horse power on 91 octane fuel.

[Brother]

That's really awesome. I bet it was fun to design that on paper and then just go to town on the build up. You must have a very fulfilling job.

If you don't mind what is the bill for something like that?

What does it cost to put MFI on an engine that didn't originally have it like an SC 3.0?

[YTNUKLR]

IMHO, that's usually something disclosed via PM/email/phone...not to be a party pOOper....I think I speak for Henry, too, when I say this.....just a kind of "etiquette thing" for the buyer/owner of the engine.

[tadd]

After doing inventory last night I 'remembered' that I have a GT3 oil pump in box for the 2.8 or 2.1LS build.

So what is the best bet for that center scavange stage? Is it as simple as rotating that section of the housing so that the inlet points upwards? I have not found flow figures, but anything to help remove that cotton candy like oil suspension that rotates with the crank would seem to be a good thing.

The other thought would be to run a 'Y' of hardline from that section of the pump up to the rear oil drain back tubes to acheive what Grady was refering to w/o using cam driven pumps a al GT3.

Thoughts anyone?

tadd

[Grady Clay]

Tadd,

Be sure to disassemble and inspect your new GT3 oil pump. About a year ago a friend found one where the original casting was improper and the subsequent machining left some untouched. It wouldn’t scavenge correctly.

Someplace in the past year or so I saw a nice CNC oil pump that could be driven off the ends of the cams (like Sporto & Turbo.)

Best,
Grady

[tadd]

Grady:
Thanks for the tip! I'll check it before it gets used.

tadd

[stownsen914]

Originally Posted by Grady Clay

I have considered doing away with the oil return tubes
and use scavenge pumps driven off the ends of the
cams (Turbo or Sportomatic) or an aftermarket pump
off the jackshaft. A small 4-section pump here could
duplicate the GT3 version simply using the oil return
tube ports in the cam housings.

I just ran across this great thread and noticed with interest the comments about running a multi-stage scavenge pump. I recall reading an article in European Car a number of years about about a car that had such a setup. It had 4 or 5 stage pump, with 3 or 4 of the stages used for scavenge. It was claimed to have the dual benefit of reducing the oil getting into the engine sump (less oil sloshing around and inducing drag), plus creating a negative air pressure situation in the crankcase (leading to reduced hp loss from windage). I can't think of the shop's name offhand who build the car, but I believe they were in Texas. The car was nicknamed Doom.

Scott

[kenikh]

These should give everyone a chubby:

http://www.barnessystems.com/8917.htm
http://www.moroso.com/catalog/categorydisplay.asp?CatCode=13939
http://www.titanspeed.com/content/pump/