Roller cams in NASCAR for 2015

[dieselgeek]

Crazy that DI doesn't seem to work as well in competition. It has done wonders for OEM applications.

On the few I've been able to tune on - the wonderful part is that there are no tricks to enrichments. Literally these do not need accel enrichments, warmup enrichments, etc. I am sure this is awesome for emissions. I'm told the problem with hotrodding a DI engine is that as soon as you increase airflow into the combustion chamber, all bets are off and you need another million dollar redesign to optimize all the parts of the combustion chamber that are required to support it.

But that was just a chat with an engineer supporting the C7R programs, it could all be BS. In my world, I get to do "a little" with a large variety of engines. One day I'd like to be able to do A LOT of studying/development on one type of engine like Warp Speed. Maybe some day.

[pamotorman]

maybe NASCAR will go to a combo of port and direct injection like the C-7R corvette race car that just won its class at the rolex 24 hour

Funny thing, talking with a GM engineer that worked on that program and asking them how to maximize power with DI - and the answer was "get rid of the DI and run port injection" !!!!!

Are you sure the DI injectors are in use on the C7R program? We were told they are NOT.

they use a combination of both port and direct. I just had a email from one of the managers of the race engine development for GM as I was wondering what they did use. they say that DI increases the low end torque and the port injection is for top end.

[dirtracr5]

I had heads off of a DI 5.3 on a 2015 Silverado last week. Alot of development went into the chamber and piston crown for sure!

[900HP]

Crazy that DI doesn't seem to work as well in competition. It has done wonders for OEM applications.

On the few I've been able to tune on - the wonderful part is that there are no tricks to enrichments. Literally these do not need accel enrichments, warmup enrichments, etc. I am sure this is awesome for emissions. I'm told the problem with hotrodding a DI engine is that as soon as you increase airflow into the combustion chamber, all bets are off and you need another million dollar redesign to optimize all the parts of the combustion chamber that are required to support it.

But that was just a chat with an engineer supporting the C7R programs, it could all be BS. In my world, I get to do "a little" with a large variety of engines. One day I'd like to be able to do A LOT of studying/development on one type of engine like Warp Speed. Maybe some day.

My only experience with modifying direct injection was a Pro-charger install on a 2014 Corvette with the LT-1 DI motor. It made 633 at the wheels on an otherwise stock unmodified Corvette. It may be the fastest most powerful street car I've ever driven, it's stupid fast. The program was just downloaded out of a hand-held unit and was not modified. This was using stock GM injectors, intake, cam, etc.

I don't even qualify for "tooner" status but I would say there was a substantial increase in airflow through this engine and it does make steam. Weather or not it would make more steam with port injection I have no idea. One thing I can say about DI is that there is a distinct advantage when you are fuel limited. DI works better with low octane fuels and high compression/boost. I believe this has to do with the piston cooling you get from vaporization. I reserve the right to be wrong.

[dieselgeek]

maybe NASCAR will go to a combo of port and direct injection like the C-7R corvette race car that just won its class at the rolex 24 hour

Funny thing, talking with a GM engineer that worked on that program and asking them how to maximize power with DI - and the answer was "get rid of the DI and run port injection" !!!!!

Are you sure the DI injectors are in use on the C7R program? We were told they are NOT.

they use a combination of both port and direct. I just had a email from one of the managers of the race engine development for GM as I was wondering what they did use. they say that DI increases the low end torque and the port injection is for top end.

My guy said they tell people that as to not offend the fans of DI and high technology. I know of another Ford-based program that did the same thing, eliminated the DI injectors altogether. This was from a friend who worked at Roush-Yates. Like Mark, I reserve the right to be wrong - it's all hearsay anyhow.

[wyrmrider]

Hard to get even atomization with late DI
Late DI is detonation suppression
Port + DI Helps if lean port injection and use DI for rich stratified charge
my version of rumors

[Amilcar]

We actually lost power going to EFI

Can you put that in perspective? Did they make no other changes to the engine combinations going to EFI? What little I know (based on interest) aobut your combos, they restrict placement of the injectors. Was that peak power you lost? or average power?

Sucks that you guys only get to tune VE tables and per cyl trims. No firmware control at all. I'd be pissed, because that's almost not EFI in my world.

diesel-
Could you please elaborate on the firmware thing?
If you can tune VE tables/ignition maps, where/how the firmware opens more possibilities?

Thanks

[140Air]

Crazy that DI doesn't seem to work as well in competition. It has done wonders for OEM applications.

I think DI has tremendous advantages in terms of efficiency and emissions, but the intake charge will always be warm and at somewhat reduced density compared to external fuel metering. This has been discussed here before. The greatest power is achieved when the fuel is introduced as far upstream as possible for maximum cooling of the charge. Another possible equally important factor for race engines is that DI injection time is extremely short at high rpms. F1 engines running at 11,000 rpm appear to need 500BAR of pressure to get full fuel delivery with DI.

[Racerrick]

The overall 24 hr Daytona winner was powered by a direct injected Ford 3.5 Eco boost using a oem F-150 block and oem ported heads.

[140Air]

The overall 24 hr Daytona winner was powered by a direct injected Ford 3.5 Eco boost using a oem F-150 block and oem ported heads.

Endurance races or any races that require multiple refueling, rely on overall performance with fuel economy as an important part. DI should be a winner, but not necessarily because of highest power.