Don Terrill’s Speed-Talk

Thought you guys may enjoy this: https://rameywomer.files.wordpress.com/ ... engine.pdf
Bore: 4.075"
Stroke: 3.185"
Displacement: 332.3
Compression Ratio: 11.75:1
Intake Valve: 2.100"
Exhaust Valve: 1.55"
Valve Lift: ~.640" on both.
Intake: Individual Throttle Body - common plenum. Varying restrictor, 2 x 35.4mm restrictors at start of 2014 season. Effective restrictor area 3.05in^2

With the 2 x 35.4mm restrictors:
600bhp SAE @ ?
460lb-ft @ 6000rpm
~300bhp @ 4000rpm
BMEP @ 6000rpm, 208.73psi (14.4bar).
Max RPM: 7500
Service Interval: 3000 miles

I got the heads off one of them things here now.
Customer got the whole engine, he's bumping it up to 6L capacity, running on E85 & using it for IPRA (Improved production road racing).
My job is to tweak the heads a little to suit an unrestricted 6L engine.

KnightEngines wrote: ↑Wed Jan 03, 2018 10:21 pm I got the heads off one of them things here now.
Customer got the whole engine, he's bumping it up to 6L capacity, running on E85 & using it for IPRA (Improved production road racing).
My job is to tweak the heads a little to suit an unrestricted 6L engine.

What are your overall impressions of what you see? Obviously, they're good pieces.


You have seen the ECR developed LT based 6.0L used in endurance racing, correct? http://www.enginelabs.com/news/cadillac ... -released/

Edited.

Please delete

this year they will use 5.5 liter engine the same as the corvette race team has been using built by the GM race shop

KnightEngines wrote: ↑Wed Jan 03, 2018 10:21 pm I got the heads off one of them things here now.
Customer got the whole engine, he's bumping it up to 6L capacity, running on E85 & using it for IPRA (Improved production road racing).
My job is to tweak the heads a little to suit an unrestricted 6L engine.

That is one thing I couldn't find in the article. What cylinder head is on these things?

CGT wrote: ↑Thu Jan 04, 2018 9:09 am

KnightEngines wrote: ↑Wed Jan 03, 2018 10:21 pm I got the heads off one of them things here now.
Customer got the whole engine, he's bumping it up to 6L capacity, running on E85 & using it for IPRA (Improved production road racing).
My job is to tweak the heads a little to suit an unrestricted 6L engine.

That is one thing I couldn't find in the article. What cylinder head is on these things?

https://m.ebay.com/itm/GM-Racing-LS7-CN ... noapp=true It’s a special GM Racing casting.

I'm designing cams for one of the competing engines, right now.
They're limited to 600hp.
The key is going to be trying to make 600hp sooner, and hold on to it longer.

hoffman900 wrote: ↑Thu Jan 04, 2018 9:36 am

CGT wrote: ↑Thu Jan 04, 2018 9:09 am

KnightEngines wrote: ↑Wed Jan 03, 2018 10:21 pm I got the heads off one of them things here now.
Customer got the whole engine, he's bumping it up to 6L capacity, running on E85 & using it for IPRA (Improved production road racing).
My job is to tweak the heads a little to suit an unrestricted 6L engine.

That is one thing I couldn't find in the article. What cylinder head is on these things?

https://m.ebay.com/itm/GM-Racing-LS7-CN ... noapp=true It’s a special GM Racing casting.

Thank you. Very interesting. Anyone know what rocker arms are required? Or do they use production LS7 pieces? I'd like to have a set of those heads for sure, I want a closer look.

CamKing wrote: ↑Thu Jan 04, 2018 10:43 am I'm designing cams for one of the competing engines, right now.
They're limited to 600hp.
The key is going to be trying to make 600hp sooner, and hold on to it longer.

Mike,

How does a cam designer go about doing that? An observation I've made is a lot of restricted engines have more exhaust duration than they would otherwise, but have less overlap.

CGT wrote: ↑Thu Jan 04, 2018 10:49 am

hoffman900 wrote: ↑Thu Jan 04, 2018 9:36 am

CGT wrote: ↑Thu Jan 04, 2018 9:09 am

That is one thing I couldn't find in the article. What cylinder head is on these things?

https://m.ebay.com/itm/GM-Racing-LS7-CN ... noapp=true It’s a special GM Racing casting.

Thank you. Very interesting. Anyone know what rocker arms are required? Or do they use production LS7 pieces? I'd like to have a set of those heads for sure, I want a closer look.

It was posted somewhere else that they use LS1 type rocker pads, but likely it's a special piece from T&D. I would imagine you could just call them up and its a standard part number.

hoffman900 wrote: ↑Thu Jan 04, 2018 10:49 am Mike,

How does a cam designer go about doing that?

This is different then a NASCAR restrictor plate engine.
These engines can make over 600hp, but are not allowed to. IMSA dyno's them.
What we've done in the past, is design the engine to make as much power as possible, and then knock the peak HP back down to the required limit.

This has been done done legally, and illegally in the past. One team, that will remain nameless, had 2 different maps. One they raced with, and one that detuned the engine by 40hp, when they dyno tested it.

CamKing wrote: ↑Thu Jan 04, 2018 12:06 pm

hoffman900 wrote: ↑Thu Jan 04, 2018 10:49 am Mike,

How does a cam designer go about doing that?

This is different then a NASCAR restrictor plate engine.
These engines can make over 600hp, but are not allowed to. IMSA dyno's them.
What we've done in the past, is design the engine to make as much power as possible, and then knock the peak HP back down to the required limit.

This has been done done legally, and illegally in the past. One team, that will remain nameless, had 2 different maps. One they raced with, and one that detuned the engine by 40hp, when they dyno tested it.

Thanks Mike. I know others who have to run with SIRs (similar design as this, just like FSAE), and was curious how you would go about designing a cam when you go from an no-restrictor to a restrictor set-up.

On the FSAE engines, we run very short exhaust durations. 20 degrees shorter then the intake.

CamKing wrote: ↑Thu Jan 04, 2018 12:06 pm

hoffman900 wrote: ↑Thu Jan 04, 2018 10:49 am Mike,

How does a cam designer go about doing that?

This is different then a NASCAR restrictor plate engine.
These engines can make over 600hp, but are not allowed to. IMSA dyno's them.
What we've done in the past, is design the engine to make as much power as possible, and then knock the peak HP back down to the required limit.

This has been done done legally, and illegally in the past. One team, that will remain nameless, had 2 different maps. One they raced with, and one that detuned the engine by 40hp, when they dyno tested it.

Who comes up with rules like this?

DaveMcLain wrote: ↑Thu Jan 04, 2018 12:36 pm

CamKing wrote: ↑Thu Jan 04, 2018 12:06 pm

hoffman900 wrote: ↑Thu Jan 04, 2018 10:49 am Mike,

How does a cam designer go about doing that?

This is different then a NASCAR restrictor plate engine.
These engines can make over 600hp, but are not allowed to. IMSA dyno's them.
What we've done in the past, is design the engine to make as much power as possible, and then knock the peak HP back down to the required limit.

This has been done done legally, and illegally in the past. One team, that will remain nameless, had 2 different maps. One they raced with, and one that detuned the engine by 40hp, when they dyno tested it.

Who comes up with rules like this?

Inlet restrictors work great when trying to equalize different engine and chassis combinations. It's just another challenge for an engine builder.

SCCA GT-Lite-GT2 uses them, FIA / IMSA / FSAE also use them.

I never understood the hate. Lots of classes with restrictions on intakes, throttle body diameters, porting, or valve size do the same thing. Eventually it chokes somewhere at some RPM and you build the motor to hold on to that power as long as possible after that point. The cylinder doesn't know where the restriction is coming from.

Only few classes, or bracket racers, can ever worry about sizing everything to whatever RPM peak they really need. Everyone else has to work around something.