Has anyone tried..?
03-18-12, 09:24 AM
#1
Has anyone tried..?
Plumbing the stock airpump into the exhaust manifold to create a secondary burn and spool the turbo? Many ECUs could control this, and you could even throw some extra fuel at the appropriate time to get the amount of expansion you wanted....
I think I have heard of people doing this with nitrous, but we already have that handy airpump...
I think I have heard of people doing this with nitrous, but we already have that handy airpump...
03-19-12, 12:26 PM
#2
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Not with the airpump, but people have done it with charge air from the turbo, as seen one some Audi rally cars from the '80s. I had done some research a while ago on the topic, and this link had some of the better pictures and descriptions. The guy actually owns (or owned) a car equipped with the system but disabled.
http://www.bufkinengineering.com/Umluft.htm
Basically the system allows intake charge air to enter the exhaust stream via the wastegate. Its controlled by vacuum pressure post TB with some other electronic vacuum control not yet determined which connects to the topside of the 944 wastegate. The wastegate will be opened at idle via vacuum pressure on the manifold or from a computer control introducing O2 in to the exhaust stream which results in a very marked increase in turbo RPMs which means more CFM airflow generated by the compressor. To prevent turbo surge the unused air that is not consumed by the engine is vented into the manifold which provides O2 gases for post combustion or a rich mix. So for example the turbocharger is always providing some very high CFM number and always rotating at high RPMs. The 944 wastegate merely dumps whatever air the engine can't consume into the hotside. The complicated part is controlling the balance between the exhaust manifold pressure and the intake manifold pressure to keep flow going in the right direction.
Described by Bruno Kreibich (2 time NA rally champ, and the guy who sold me the car), A car so equiped would idle at about 4000 rpms. Boost pressure is instant and power is fantastic with NO lag at all at any RPM. The problems encountered is that the system burns up exhaust valves and exhaust manifolds rapidly. Bruno said within an hour.
03-19-12, 05:37 PM
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the air pump air goes to the exhaust ports stock, so i'm going to say no, its not big enough to do much?
03-20-12, 06:48 AM
#4
Unless I am mistaken, the main part of the flow goes to the converter, and in any case the airpump in stock form only operates within a certain RPM range and below a certain load point.
That is an interesting idea about using charge air, but I would be worried about reversion of that flow. With an airpump this wouldnt be an issue. I'm too lazy to do an estimate, but it wouldnt take much flow to get the mixture in the manifold back to where it could burn...
That is an interesting idea about using charge air, but I would be worried about reversion of that flow. With an airpump this wouldnt be an issue. I'm too lazy to do an estimate, but it wouldnt take much flow to get the mixture in the manifold back to where it could burn...
03-20-12, 11:40 AM
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This particular system though, afaik, was used to keep the turbo RPM high during off load, transient driving. Slightly different from using it as a spooling aid which I think is what you're after.
03-20-12, 11:56 AM
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Unless I am mistaken, the main part of the flow goes to the converter, and in any case the airpump in stock form only operates within a certain RPM range and below a certain load point.
That is an interesting idea about using charge air, but I would be worried about reversion of that flow. With an airpump this wouldnt be an issue. I'm too lazy to do an estimate, but it wouldnt take much flow to get the mixture in the manifold back to where it could burn...
That is an interesting idea about using charge air, but I would be worried about reversion of that flow. With an airpump this wouldnt be an issue. I'm too lazy to do an estimate, but it wouldnt take much flow to get the mixture in the manifold back to where it could burn...
the stock system has some timers, so it might not go to port air right when you close the throttle, but its close.
anyways, try it, all the hardware is there, all you need to to is have control over the 2 solenoids
03-20-12, 12:12 PM
#7
the FD also cuts off the pump after 3k, but not difficult to manually wire it to run longer for testing purposes.
but i seriously doubt there's noticable gains from this, the pump being driven would probably negate the very minor spooling effects if there is any at all.
but i seriously doubt there's noticable gains from this, the pump being driven would probably negate the very minor spooling effects if there is any at all.
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