what do you think ??

[Clem Z.]

remember years ago when the chevy powered can am engine had 2 different length injector stacks and it was said that was to increase the torque. i wonder what they would say about this new corvette daytona prototype injection system ? i believe the old can am engine had the 2 different length stacks was because on those BBC heads 2 intake ports turned into the center of the chamber and had better flow and 2 intake port turned into the chamber wall so they compensated with the different length stacks. these stacks are cut to clear the sloping back window of the race car. the difference is because electronic FI can be tailored for different A/F ratio in each cylinder where the mechanical FI could not.

[Gary B.]

Re: what do you think ??

Thanks for the photo.
I hope I can watch the 24 hour race on the internet.

[Stuart F.]

Re: what do you think ??

With the extra interest generated by this new Corvette Daytona, I may just take a drive over there this year for the race. It is just a short drive for us, and I am going over this weekend for the Turkey Run car show/swap meet (one of the biggest in the country.

Clem; are you coming to the PRI show this year?

Wish I was about 20 years younger so I could enjoy all the car things central Florida has to offer. As it is now, I'm thinking I may need to get me a scooter, Ha!

Stu Fox

[Steven B.]

Re: what do you think ??

'Went to Elkhart Lake Can Am during late 60's and met an engineer from Gulf who worked on the design of the velocity stacks for the McLaren cars. He said a number of tests were performed to tune HP and torque to specific courses and that Elkhart was a real challenge in that the combination of turns and the long Thunder Valley straight resulted in alot of compromise. (Side note---met him in a bar in Sheboygan Falls. I got one of about 12 cots above the bar for $5.00 a night that included a bathtub in the middle of the room with only cold water. Other than being thrown down the stairs in my sleep during the early morning by a drunk construction worker it was worth the five bucks. On the up side the engineer gave us access to the paddock and pits during the race. The brats and corn on the cob were great there.)

Steve

[Duke W.]

Re: what do you think ??

My understanding is that the two different length stacks on the Can-Am engines smoothed out the torque curve, which on a high specific power output engine, i.e. long duration, high overlap cam, can be pretty bumpy.

The graduated length stacks on the new Daytona prototype engine will tend to flatten the torque curve since the short stacks will increase torque at higher revs and the long stacks will increase torque at lower revs. Peak torque will be less than if all stacks were the same, long length, and peak power will be less than if all stacks were the same, short length, but torque/power bandwidth is broadened.

On a road racing engine the goal is to maximize average power in the rev range that is determined by shift point and gear ratio spacing rather than peak power.

For example, if peak revs are 7000 and intergear ratios are 1.25, then revs will drop to 7000/1.25 = 5600 at each shift, so final tuning should be accomplished to maximize average power from 5600 to 7000.

Given the high flow coefficient of the LS engine head ports and the fact that for endurance racing revs must be kept at a moderate level to ensure longevity, this engine probably has pretty conservative valve timing relative to traditional Gen I small block racing engines and current unrestricted Sprint Cup engines that rev to about 9500.

BTW, Clem, do you have any data on this engine - bore, stroke, displacment, and peak torque and power ratings?

Duke

[Clem Z.]

Re: what do you think ??

With the extra interest generated by this new Corvette Daytona, I may just take a drive over there this year for the race. It is just a short drive for us, and I am going over this weekend for the Turkey Run car show/swap meet (one of the biggest in the country.

Clem; are you coming to the PRI show this year?

Wish I was about 20 years younger so I could enjoy all the car things central Florida has to offer. As it is now, I'm thinking I may need to get me a scooter, Ha!

Stu Fox

no not coming to Fla. this winter. going to stay home and watch it snow.

[Clem Z.]

Re: what do you think ??

My understanding is that the two different length stacks on the Can-Am engines smoothed out the torque curve, which on a high specific power output engine, i.e. long duration, high overlap cam, can be pretty bumpy.

The graduated length stacks on the new Daytona prototype engine will tend to flatten the torque curve since the short stacks will increase torque at higher revs and the long stacks will increase torque at lower revs. Peak torque will be less than if all stacks were the same, long length, and peak power will be less than if all stacks were the same, short length, but torque/power bandwidth is broadened.

On a road racing engine the goal is to maximize average power in the rev range that is determined by shift point and gear ratio spacing rather than peak power.

For example, if peak revs are 7000 and intergear ratios are 1.25, then revs will drop to 7000/1.25 = 5600 at each shift, so final tuning should be accomplished to maximize average power from 5600 to 7000.

Given the high flow coefficient of the LS engine head ports and the fact that for endurance racing revs must be kept at a moderate level to ensure longevity, this engine probably has pretty conservative valve timing relative to traditional Gen I small block racing engines and current unrestricted Sprint Cup engines that rev to about 9500.

BTW, Clem, do you have any data on this engine - bore, stroke, displacment, and peak torque and power ratings?

Duke

5 L,530 HP@ 7000,450# ft @ 5500

[Gene M.]

Re: what do you think ??

It just sounds a bit weird having different cylinders producing at different power levels. I would think that one would prefer all be equal as possible.......no?

[Clem Z.]

Re: what do you think ??

the cylinder heads are the direct injection ones to be used on the C-7 corvette.

[Steven B.]

Re: what do you think ??

My understanding is that the two different length stacks on the Can-Am engines smoothed out the torque curve, which on a high specific power output engine, i.e. long duration, high overlap cam, can be pretty bumpy.

The graduated length stacks on the new Daytona prototype engine will tend to flatten the torque curve since the short stacks will increase torque at higher revs and the long stacks will increase torque at lower revs. Peak torque will be less than if all stacks were the same, long length, and peak power will be less than if all stacks were the same, short length, but torque/power bandwidth is broadened.

On a road racing engine the goal is to maximize average power in the rev range that is determined by shift point and gear ratio spacing rather than peak power.

For example, if peak revs are 7000 and intergear ratios are 1.25, then revs will drop to 7000/1.25 = 5600 at each shift, so final tuning should be accomplished to maximize average power from 5600 to 7000.

Given the high flow coefficient of the LS engine head ports and the fact that for endurance racing revs must be kept at a moderate level to ensure longevity, this engine probably has pretty conservative valve timing relative to traditional Gen I small block racing engines and current unrestricted Sprint Cup engines that rev to about 9500.

BTW, Clem, do you have any data on this engine - bore, stroke, displacment, and peak torque and power ratings?

Duke

Duke, been out for Thanksgiving a few days. You are correct in your interpretation of the different length stacks. That is exactly what I was told by the Gulf engineer. Different length stacks were used at different tracks depending on HP vs Torque requirements and track design.

Steve

[Clem Z.]

Re: what do you think ??

Duke, been out for Thanksgiving a few days. You are correct in your interpretation of the different length stacks. That is exactly what I was told by the Gulf engineer. Different length stacks were used at different tracks depending on HP vs Torque requirements and track design.

Steve

different lengths produce different torque curve but i was referring to the fact they had 2 different lengths tubes on same engine,2 shorter than the other 2 on each head. there was once a story that different length header pipes on the same header would be better for the power spread but i read a article where they tried this and it was worse than equal length tubes. if katech did the engine i will call and see what they say.

[Steven B.]

Re: what do you think ??

different lengths produce different torque curve but i was referring to the fact they had 2 different lengths tubes on same engine,2 shorter than the other 2 on each head. there was once a story that different length header pipes on the same header would be better for the power spread but i read a article where they tried this and it was worse than equal length tubes. if katech did the engine i will call and see what they say.

You are right. I should have been more clear. (I guess my wife is right that what I think isn't what I say.) There were 2 different lengths on each head, 2 long, 2 short. I need to check my old pics. but IIRC it was the same on McLaren's and Penske's Lola at Mid Ohio, also.

Steve

[Michael H.]

Re: what do you think ??

different lengths produce different torque curve but i was referring to the fact they had 2 different lengths tubes on same engine,2 shorter than the other 2 on each head. there was once a story that different length header pipes on the same header would be better for the power spread but i read a article where they tried this and it was worse than equal length tubes. if katech did the engine i will call and see what they say.

GM/engineering mentioned that the different length injector tubes were used because of the different length/flow rates of the two different design intake ports in the heads.
I have some GM paperwork on this, somewhere. Clem, you probably do too if you were fooling around with Can-AM stuff back then.

[Clem Z.]

Re: what do you think ??

i got this reply back from my contact at GM racing. Clem,

The different length stacks allow the engine to "tune up" over a wider engine speed range giving a broader torque curve.

JC

[Bill H.]

Re: what do you think ??

A guy here has these on his McLaren .