Remapping a supercharged engine
Discussion
This one is bugging me because I don't understand where the gains come from.
Turbo engine - presumably the mapper would increase the boost and write fuel maps to suit ?
Supercharged - isn't the boost level fixed by the max speed of the engine because it's driven by a belt ?
I know one or both pulleys can be changed to increase the SC speed, I guess that must give more boost but the remap sites (many of them) don't mention any mechanical work required for their remaps.
Gains do seem to be smaller than with turbo engines but still worth having & certainly more than N/A engines.
Hopefully somebody on here is a remap expert who can put me out of my misery
Turbo engine - presumably the mapper would increase the boost and write fuel maps to suit ?
Supercharged - isn't the boost level fixed by the max speed of the engine because it's driven by a belt ?
I know one or both pulleys can be changed to increase the SC speed, I guess that must give more boost but the remap sites (many of them) don't mention any mechanical work required for their remaps.
Gains do seem to be smaller than with turbo engines but still worth having & certainly more than N/A engines.
Hopefully somebody on here is a remap expert who can put me out of my misery
What kind of supercharger?
The basic idea is the same as a turbocharged engine. More boost + more fuel = more power.
Some superchargers have bleed of setups to limit boost, others need, as you said, smaller pulleys etc.
A good mapper will tweak the AFR and timing etc to get the most out of a setup.
I got an extra 60bhp from one map to another with just a change of exhaust and a good mapper!
The basic idea is the same as a turbocharged engine. More boost + more fuel = more power.
Some superchargers have bleed of setups to limit boost, others need, as you said, smaller pulleys etc.
A good mapper will tweak the AFR and timing etc to get the most out of a setup.
I got an extra 60bhp from one map to another with just a change of exhaust and a good mapper!
unclegrouch said:
Thanks for the reply.
Yep I know the basic concept is to force more air into the engine but wasn't aware SC's had any kind of bleed to divert excess boost.
So a mapper could tweak the boost without changing pulleys . ......... interesting
Positive displacement superchargers will be making more boost than the engine requires for a chunk of the rev range so it is quite common for the throttle body to have a double butterfly setup at 90* angle to each other. One is linked to the intake manifold often the larger portion and the lower butterfly goes back into a boost return system. As the throttle opens the boost return closes. It is possible to change the ratio of the opening/closing allowing more boosted air in to go with extra fuel & ignition adjustments. Yep I know the basic concept is to force more air into the engine but wasn't aware SC's had any kind of bleed to divert excess boost.
So a mapper could tweak the boost without changing pulleys . ......... interesting
unclegrouch said:
Doesn't that over speed the SC when the engine revs are very high ?
Manufactures build in quite a safety margin. There are chargers that can handle 20,000 rpm which are run at 12,000 rpm max on a engine with a 6,000rpm limit which gives a 2:1 ratio. Changing the pulley size to spin the charger to 3:1 engine speed would take max charger speed to 18,000rpm. This would still be within safe operating range but would hugely reduce the service intervals of the charger whilst providing significantly more boost!!!!aka_kerrly said:
Positive displacement superchargers will be making more boost than the engine requires for a chunk of the rev range so it is quite common for the throttle body to have a double butterfly setup at 90* angle to each other. One is linked to the intake manifold often the larger portion and the lower butterfly goes back into a boost return system. As the throttle opens the boost return closes. It is possible to change the ratio of the opening/closing allowing more boosted air in to go with extra fuel & ignition adjustments.
Great explanation, thank you - I had no idea about the boost management on supercharged engines (I knew a wastegate as such wasn't possible). So a light map would be a good option aka_kerrly said:
Manufactures build in quite a safety margin. There are chargers that can handle 20,000 rpm which are run at 12,000 rpm max on a engine with a 6,000rpm limit which gives a 2:1 ratio. Changing the pulley size to spin the charger to 3:1 engine speed would take max charger speed to 18,000rpm. This would still be within safe operating range but would hugely reduce the service intervals of the charger whilst providing significantly more boost!!!!
Even more good news So just changing one pulley & aiming for 10-12% overdrive isn't going to make it self destruct thanks againThe Rotrex Kid said:
It’s a calculation of trying to hit the peak charger speed at the revs you want it to. Mine hits top speed at 7800rpm
That sounds sensible & with the margins explained above, I guess going over the peak isn't going to do any damage.Thanks for your input
7800 rpm ......... What is it, sounds a real screaming demon ?
Edited by unclegrouch on Tuesday 15th February 18:04
unclegrouch said:
The Rotrex Kid said:
It’s a calculation of trying to hit the peak charger speed at the revs you want it to. Mine hits top speed at 7800rpm
That sounds sensible & with the margins explained above, I guess going over the peak isn't going to do any damage.Thanks for your input
7800 rpm ......... What is it, sounds a real screaming demon ?
Edited by unclegrouch on Tuesday 15th February 18:04
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