Peak Hp/Torque and Stress on the motor

[Guest prescience]

Here's a thread which considers the stress on the engine at peak torque and peak power and the differences between them - amongst other things

 

Its pretty heavy going in the later stages and you can see my contribution mid-evening on New Years Eve (which was ignored LOL).

 

Concentrate on the posts by RESOLUTE he's an automotive engineer and knows his stuff - initially his views were derided but finally accepted.

 

If you understand all the stuff on pages 4 and 5, you're a better man than me

 

http://www.my350z.com/forum/showthread.php?t=161763

[hagar]

so after attempting two pages (good read!) does adding FI to the 350z pose any real problems?

[Guest prescience]

yes and no.

 

If it is done correctly, then with luck, you will have thousands of miles with smiles; but there is a risk of course in boosting an engine not designed for FI.

 

You can reduce or minimise the additional risk, but never eliminate it.

 

Of course, it is quite possible to blow a motor NA

 

There is a lot of information in the US and detailed research is a must along with knowing what you want to achieve performance and driveability wise

[g_torphins]

you can see my contribution mid-evening on New Years Eve (which was ignored LOL).

 

Classic.I've had a couple of those over there

 

......so anyway............

[Traktion]

Interesting thread that!

[SkylineV35]

Wow first page and headache.. lol But good info!

[Tricky-Ricky]

Makes no sense to me, not sure about his maths, but to me, the motor pushing more power at lower RPM would be the less stressed due to the fact that the faster the moving parts are, the more stress they generate, both dynamically and harmonically, regardless of BHP or torque.

 

[Mark@Abbey m/s]

more power/torque at lower RPM is going to stress the components more (rods/pistons) due to cylinder pressure and the RPM (lower RPM means the motor is seeing peak cylinder pressure for longer) Cylinder pressure is higher when a motor is making the peak torque higher RPM means peak cylinder pressure is lower and sees the peak cylinder pressure for a shorter time.

 

This is the issue with the DE/REV UP VQ motors and the weak con rods

 

If you turbo the motors on stock rods when your in a big gear (5th/6th) cruising on the motor way you open the throttle car makes full boost very quickly due to load but accelerates slowly so seeing peak torque=high cylinder pressure for a long time and this will cause the con-rods to fail. If the car was SC this wouldn't happen as boost is in relation to RPM but once the motor is making higher RPM the motor sees peak torque later on in the RPM range.

 

This is why we  can tune a SC car to over 400+ bhp on a stock DE/REV UP motor but we tune the torque out of the turbo car to make it safe.

[nissanman312]

Thanks for that explanation  mark I was just reading about a guy that blew his tt 370z in America and said it  blew labouring the engine in 6 th ...i thought it was strange but that explains it

[Tricky-Ricky]

That's odd! I have always been under the opposite impression, as per graph?

 

[Mark@Abbey m/s]

Peak cylinder pressure will be around max torque which looking at the above graph will be around 3000rpm