N-Tune
07-19-2011, 03:09 AM
#48
Rainman
Rennlist Member
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Would there be any pipe option available for those that wish to dump the stock airbox altogether? It is a large, somewhat heavy box that just cancels the nice intake noise. A pipe running from the manifold straight to the snorkel inlet would be sweet.
07-19-2011, 07:20 AM
#50
A piece that allows for the stock airbox also allows for a "snorkel" if you want it. You should also start to question the stock manifold/throttle/jboot installation - what might be better than that? I think ITB's are worth it (bike throttles) - but as Josh and I have discussed, they don't always work great with SD tuning because a slight opening of the throttle greatly reduces the vacuum that the MAP sensor sees. In general you see a drop in sensor resolution as any throttle opening beyond that is operating over less difference in vacuum.
The next piece of the puzzle is equally tricky. Generally speaking we want the intake with the most equal runners (of the correct length for peak RPM) and the straightest path for the air. Different lengths of intake runner tune for different RPM because air is elastic - it stretches as the valve opens and pressure drops and rebounds, in a wave, as the valve closes. That wave resonates within the chamber of the intake runner - and when the intake valve opens/closes at the right speed it allows the rebounding charge (standing wave in the inlet runner) into the cylinder just at the right time, meaning the air moving toward and into the cylinder is moving faster, which in turn leads to a greater cylinder filling. This is good, it leads to a natural supercharging effect. But with a fixed length of runner it only happens optimally at a certain RPM. This is why 964 and after NA 911's have the varioram system.
Varioram is a 2 stage system which opens flaps (basically) to change the length of the runner to give a high RPM and low RPM optimised position. However, if we think of a trombone we can think of a way that the intake can be optimised in infinite degrees to provide the precise resonant frequency to induce a charging effect at a certain RPM. It is possible to build an intake like this - Mazda did it for a Le Mans car, but it's tricky and would require it's own electronics to control the length of the intake - for example, as you shift gear the rpms drop and the box of tricks would have to contract the intake to match.
So, what about something more practical? Well, the stock NA intake is pretty weird - with the jboot bend and strangely twisted runners - maybe they had a plan, but I think that an equal length four-runner plenum with the inlet central to the plenum could be better, now that we're doing away with the AFM and airbox... The length of the runner could be better tuned to the RPM you wish to boost - and the anecdotal evidence suggests that stock 944 valvetrains can handle up to 7000 rpm before float becomes an issue.
Just a thought - but basically want to point out one thing, the SD tune (and DME stuff in general) that Rogue is putting together gives us a new canvas for these cars - particularly the NA 8v and 16v cars.
The next piece of the puzzle is equally tricky. Generally speaking we want the intake with the most equal runners (of the correct length for peak RPM) and the straightest path for the air. Different lengths of intake runner tune for different RPM because air is elastic - it stretches as the valve opens and pressure drops and rebounds, in a wave, as the valve closes. That wave resonates within the chamber of the intake runner - and when the intake valve opens/closes at the right speed it allows the rebounding charge (standing wave in the inlet runner) into the cylinder just at the right time, meaning the air moving toward and into the cylinder is moving faster, which in turn leads to a greater cylinder filling. This is good, it leads to a natural supercharging effect. But with a fixed length of runner it only happens optimally at a certain RPM. This is why 964 and after NA 911's have the varioram system.
Varioram is a 2 stage system which opens flaps (basically) to change the length of the runner to give a high RPM and low RPM optimised position. However, if we think of a trombone we can think of a way that the intake can be optimised in infinite degrees to provide the precise resonant frequency to induce a charging effect at a certain RPM. It is possible to build an intake like this - Mazda did it for a Le Mans car, but it's tricky and would require it's own electronics to control the length of the intake - for example, as you shift gear the rpms drop and the box of tricks would have to contract the intake to match.
So, what about something more practical? Well, the stock NA intake is pretty weird - with the jboot bend and strangely twisted runners - maybe they had a plan, but I think that an equal length four-runner plenum with the inlet central to the plenum could be better, now that we're doing away with the AFM and airbox... The length of the runner could be better tuned to the RPM you wish to boost - and the anecdotal evidence suggests that stock 944 valvetrains can handle up to 7000 rpm before float becomes an issue.
Just a thought - but basically want to point out one thing, the SD tune (and DME stuff in general) that Rogue is putting together gives us a new canvas for these cars - particularly the NA 8v and 16v cars.
07-19-2011, 11:33 AM
#53
Race Car
The STD kit will be using a 1bar sensor so you can't really use that for any boosted application. However, Josh will be helping me out tuning my 83 sc car using a 2 or 2.5 bar sensor so hopefully some data can be accumulated to help others out.
07-19-2011, 01:13 PM
#54
Rainman
Rennlist Member
Rennlist Member
So, what about something more practical? Well, the stock NA intake is pretty weird - with the jboot bend and strangely twisted runners - maybe they had a plan, but I think that an equal length four-runner plenum with the inlet central to the plenum could be better, now that we're doing away with the AFM and airbox... The length of the runner could be better tuned to the RPM you wish to boost - and the anecdotal evidence suggests that stock 944 valvetrains can handle up to 7000 rpm before float becomes an issue
but for the plenum/equal runners/central inlet, have you looked at the lindsey manifold? very pretty
and they say it will pretty much outflow any head you put on there.
07-26-2011, 12:33 PM
#56
Race Car
Josh is pretty busy at the moment preparing for marriage. I'm sure once he gets back at it, it won't take long. We spoke last night and it sounds like we will be out tuning around soon enough.
07-26-2011, 02:37 PM
#57
What would be cool with this is if you could take the turbo intake and TB, then hook up Rogue's pipe, and then route an intake pipe with a cone filter to the front corner of the engine bay so it can suck in all the cold air. With the turbo manifold, if the TPS from the NA will hook up, there would be a straight shot from the TB to the fender removing any restriction caused by the J pipe. It'd probably clean up the engine bay pretty nicely too.
07-26-2011, 07:24 PM
#58
Addict
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Small Business Partner
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What would be cool with this is if you could take the turbo intake and TB, then hook up Rogue's pipe, and then route an intake pipe with a cone filter to the front corner of the engine bay so it can suck in all the cold air. With the turbo manifold, if the TPS from the NA will hook up, there would be a straight shot from the TB to the fender removing any restriction caused by the J pipe. It'd probably clean up the engine bay pretty nicely too.
