GTR Forum banner

21 - 40 of 45 Posts

·
Skyline Section Manager
Joined
·
11,872 Posts
Wonder why they used a belt instead of a chain, there must have been some advantage because the RB is based on an L series and the L series used a chain so seems weird why they would skimp on an engine as complicated as an RB26.
Probably cost and reliability.
I would like to see a gear driven conversion. That would be very cool.
 

·
Registered
Joined
·
484 Posts
Discussion Starter #22
Surely chains are quite reliable? Belts can snap and while chains also wear I'd have thought they are generally pretty strong. Belt must be cheaper though, just seems weird as the RB isn't really a cheap engine, twin turbo and ITB's etc.



Gear conversion would be cool, like the one OS Giken do for the L series:




 

·
Registered
Joined
·
591 Posts
That great conversion looks cool but horrendously inefficient! Would that be run dry as well or have they modified the oil path as well to run them wet?
 

·
Registered
Joined
·
593 Posts
I know that timing belt design is worse for accurate timing but there benefits to a belt over gears or a chain.
They don't transmit harmonics through the engine and they have a lot less rotational mass.
 

·
Skyline Section Manager
Joined
·
11,872 Posts
As shown on the CAS, cam timing can change by over 5 degrees. If you were to tune an engine to its optimum tune, then alter the cam timing by 5 degrees, you might loose 20hp.
With gears this will not happen. Chains stretch but belts do not.
I would think gears might be the most efficient too. Everything rolls with gears, there is no rubbing, unlike a belt or chain.
 

·
Registered
Joined
·
593 Posts
Do you think that cam timing alone can loss 20hp, even if you have a crank trigger?
I suppose it would be hard determine the power loss due to the extra rotational mass of the gears.
 

·
Skyline Section Manager
Joined
·
11,872 Posts
20hp is a total finger in the air figure. The gain is what you would loose with camshaft timing scatter. Which is evident on the CAS. This error is regardless of where you read ignition timing. This is a mechanical variation.
 

·
Registered
Joined
·
56 Posts
Do you think that cam timing alone can loss 20hp, even if you have a crank trigger?
I suppose it would be hard determine the power loss due to the extra rotational mass of the gears.
No you wouldn't have a problem with a crank trigger because it would read the timing.
20hp or not I wouldn't want to see what happens on 8000+ rpm and 2bar boost with a 5 degree change
 

·
Registered
Joined
·
484 Posts
Discussion Starter #29
That great conversion looks cool but horrendously inefficient! Would that be run dry as well or have they modified the oil path as well to run them wet?
Don't think its inefficient, that engine makes huge power, 3.2L and it makes 420 @ 9000rpm and 392NM on carbs with a 10,000rpm redline.

Pretty sure it runs dry.
 

·
Registered
Joined
·
1,678 Posts
Piggaz, is you new trigger setup a 36-1 wheel at the crank? hall effect sensor? no cam sensor?
I do still have the OEM CAS, but I believe it is used only for starting (IE the initial phasing of the engine to start quicker). I did have the option to delete it though.

The the wheel is on the back of the balancer. Belew are some photo's.






Rear of the wheel.

Trigger sensor and wheel.
 

·
Registered
Joined
·
4,586 Posts
Best to run the CAS sensor as well, something to do with seq spark and avoiding having to run group fire injection.....I'd have to check with the boss, we have a modification that we do for the factory CAS to run a lesser number wheel in it.
 

·
Registered
Joined
·
752 Posts
piggaz could you please ask your tuner if he is using the cas just for starting? or is it using cam signal for sequential firing of inj and ign?
 

·
Registered
Joined
·
2,638 Posts
Best to run the CAS sensor as well, something to do with seq spark and avoiding having to run group fire injection.....I'd have to check with the boss, we have a modification that we do for the factory CAS to run a lesser number wheel in it.
The cam sensor is only used during cranking to identify which firing stroke the bottom end is on (as the crank spins twice for every cam rotation) (when used with a crank based system)

The AMT setup for cam sensor is over the top in my opinion and gives no benefit as once you run a crank wheel the cam sensor has no effect to ignition timing. It also looks messy

I really like the crank sensor kits (like amt) combined with changing the disc In The cas to suit use as a cam sensor for synchronisation. I know Greg at Protuner sells the timing discs, it then also looks right.
 

·
Registered
Joined
·
593 Posts
I will bow down to the tuners expertise, but I would have thought that it would depend on the implementation of the ECU as to whether a 720 sync is acquire during started and then the CAM signal ignored.
The CAM signal is certainly not used for triggering the spark or anything like that, so not critical in terms of accurate timing. But it could be used to ensure that the engine is still in 720 sync while it is running, not sure that's necessary though.
 

·
Registered
Joined
·
2,638 Posts
I will bow down to the tuners expertise, but I would have thought that it would depend on the implementation of the ECU as to whether a 720 sync is acquire during started and then the CAM signal ignored.
The CAM signal is certainly not used for triggering the spark or anything like that, so not critical in terms of accurate timing. But it could be used to ensure that the engine is still in 720 sync while it is running, not sure that's necessary though.
If your running sequential the cam sensor must be used during syn, if batch fired it won't be.

I am not aware of any ecu that uses cam signal when running for any compensation. The only possible use is disgnostics as in cambelt replaced with wrong crank/cam alignment.

The problem is many tuners don't understand how the cam sensor is used, therefore can't answer your questions. You really got to be involved in ecu design and software writing to understand how the raw signals are processed
 

·
Registered
Joined
·
752 Posts
you mean the stock 6 slot signals couldnt be used for cam position signal (for sequential firing of both inj and ign? why?
I would like to buy the toothed damper wheel for crank position signals and use the stock cas for cam position(phase). Of course only one of the optical sensors (the 6 slots one) would be chosen for cam signal.
 
21 - 40 of 45 Posts
Top