[DGthe3]

Originally Posted by ChefBorOzzy

Never noticed the "attachment" icon on here before.. Lol.

Thanks for the upload.

Originally Posted by hotlap

Help. I see two different direct injection types listed. SIDI and DI. What is the difference?

Thanks for the PDF Chef

No difference between them. SIDI is Spark Ignition Direct Injection. The Spark Ignition part often gets dropped because its pretty much redundant when talking about a gasoline engine.

[Mr Twisty]

The old LT5 was 7200 rpm... it was 350 ci but best I recall it was long stroke. That's a good sign for a modern 6.2 L

[doc7000]

Originally Posted by Mr Twisty

The old LT5 was 7200 rpm... it was 350 ci but best I recall it was long stroke. That's a good sign for a modern 6.2 L

During the development of the LT5 engine first GM wanted to develop a DOHC head for the small block engine. Lotus convinced GM to allow them to make a ground up design, they were aiming for about 400BHP, though they wanted a bigger bore spacing then 4.4 inches and GM said no (so they can market it as a small block chevy). Because of that Lotus could only promise 375BHP and 370ft-lbs. with further development they got to 405BHP and 385ft-lbs.

Contributing factors in the downfall of the LT5 engine was because of the Gen III SBC, during the production of the LT5 engine they were pushing prototype LS1 5.7L engines to 400BHP. The LT5 engine was physically much bigger and heavier then the LS1 engine, also the C5 engine bay wasn't made big enough to fit the LT5 engine in it. 345BHP LS1 C5s were running faster lap times then the ZR1 Corvette during the C5 developments. Also toward the end due to poor sales of the ZR1 Corvette it made GM feel that there wasn't really a market for a higher priced Corvette. This is why they were developing a entry level FRC Corvette that at first had cloth seats and roll up windows. The C5 Corvette ended up moving well and the FRC Corvette which had some luxury items put back in it wasn't selling well. So they finally put that 400BHP 5.7L engine into production in the form of the C5 Z06 Corvette.

The LT5 engine is a cool looking engine and when it was put into production there wasn't many normally aspirated engines producing that much power. It was really at the start of normally aspirated engines making a come back, driving a C4 ZR1 Corvette back in 1990 probably was an amazing experience. However what the C5 Z06 showed was more important then just having an engine you really needed the whole package. The C5 Z06 produced the same power as the C4 ZR1 yet while being smaller and lighter with a better weight split. The C4 ZR1 was 3,465 pounds while the C5 Z06 was 3,118 pounds, for a performance car I think it is obvious that the C5 Z06 is better though when it comes to fun that is up for grabs.

[BradfordCamaro]

Now lets start guessing potential RPM and power figures based on this new info.

[NemesisC5]

Don't completely rule out flat plane crank if they do indeed produce DOHC V8. Mustang has done quite well with the flat plane crank Voodoo and it's high rpm capability.

[TLSTWIN]

Originally Posted by NemesisC5

Don't completely rule out flat plane crank if they do indeed produce DOHC V8. Mustang has done quite well with the flat plane crank Voodoo and it's high rpm capability.

Would be interested in seeing how well/long the ford voodoo flat plane crank engine handles heat. that motor has to be kept at higher rpms to stay in the power band, which creates a potential high under hood temps scenario. not a good idea for GM since they had some issues with the LT4 that they have worked through. it would be a black eye to potentially have another motor have overheating issues.... of course this could be a mute point if they already figured it out or the motor doesnt have that problem.

[Bhobbs]

6.2 liters is way too big for a FPC. Ford had to do a lot of work to keep the 5.2 from vibrating itself to pieces.

[DGthe3]

Originally Posted by TLSTWIN

Would be interested in seeing how well/long the ford voodoo flat plane crank engine handles heat. that motor has to be kept at higher rpms to stay in the power band, which creates a potential high under hood temps scenario. not a good idea for GM since they had some issues with the LT4 that they have worked through. it would be a black eye to potentially have another motor have overheating issues.... of course this could be a mute point if they already figured it out or the motor doesnt have that problem.

Moot -minimal value or relevance (pronounced 'moo-t')
Mute -silent (pronounced 'mew-t')

Anyways, keeping an engine cool is pretty much dependent on 2 things: how much power is it making & how much airflow is it getting (well, ambient temperatures too but engineers can't control that ... yet!). Whether its forced induction or NA doesn't really matter.

Originally Posted by Bhobbs

6.2 liters is way too big for a FPC. Ford had to do a lot of work to keep the 5.2 from vibrating itself to pieces.

Beat me to it. As displacement increases, vibrations become very difficult to manage in a flat plane crank V8 -which is why you rarely see them in large engines. 5 or so litres is practical limit for flat plane V8s. The Voodoo is the largest production FPC engine, and as I understand it Ford had to do quite a bit of finagling to get it to behave itself. Adding another litre on top of that would require restricting the rpms to such a degree that it makes it utterly pointless to use a flat plane.

[NemesisC5]

Originally Posted by Bhobbs

6.2 liters is way too big for a FPC. Ford had to do a lot of work to keep the 5.2 from vibrating itself to pieces.

Originally Posted by DGthe3

Beat me to it. As displacement increases, vibrations become very difficult to manage in a flat plane crank V8 -which is why you rarely see them in large engines. 5 or so litres is practical limit for flat plane V8s. The Voodoo is the largest production FPC engine, and as I understand it Ford had to do quite a bit of finagling to get it to behave itself. Adding another litre on top of that would require restricting the rpms to such a degree that it makes it utterly pointless to use a flat plane.

Ahh...thanks for the correction. Didn't have a clue but now that it's been pointed out I can easily see it.

[Bhobbs]

FPC isn't necessary for high revs, it just makes it easier to spin the engine fast. Plus, it has some benefits over CPC, like engine breathing because of the firing order.

The 6.2 M159 revved to 8,000 rpm with a CPC.

[TLSTWIN]

Originally Posted by DGthe3

Moot -minimal value or relevance (pronounced 'moo-t')
Mute -silent (pronounced 'mew-t')

Anyways, keeping an engine cool is pretty much dependent on 2 things: how much power is it making & how much airflow is it getting (well, ambient temperatures too but engineers can't control that ... yet!). Whether its forced induction or NA doesn't really matter.


Beat me to it. As displacement increases, vibrations become very difficult to manage in a flat plane crank V8 -which is why you rarely see them in large engines. 5 or so litres is practical limit for flat plane V8s. The Voodoo is the largest production FPC engine, and as I understand it Ford had to do quite a bit of finagling to get it to behave itself. Adding another litre on top of that would require restricting the rpms to such a degree that it makes it utterly pointless to use a flat plane.

Thanks for the grammar fix, can't catch everything.

But we will have to agree to disagree on there only being 2 things dependent on keep it cool, there are much more variables than that. rpms, friction, and oil are just a few.

[Zeke.Malvo]

Originally Posted by Bhobbs

FPC isn't necessary for high revs, it just makes it easier to spin the engine fast. Plus, it has some benefits over CPC, like engine breathing because of the firing order.

The 6.2 M159 revved to 8,000 rpm with a CPC.

Please explain "spin the engine fast". Do you mean make more powet? Because, beside gearing, more power will make an engine spin faster.

[fradaj]

Originally Posted by Zeke.Malvo

Please explain "spin the engine fast". Do you mean make more powet? Because, beside gearing, more power will make an engine spin faster.

A FPC is usually lighter allowing it to rev faster.

[Bhobbs]

Originally Posted by Zeke.Malvo

Please explain "spin the engine fast". Do you mean make more powet? Because, beside gearing, more power will make an engine spin faster.

The FPC is generally lighter, but in the case of the Voodoo, its only a few lbs. That decreased weight is easier to accelerate, just like a car would be, so the engine revs up faster.