gen1 m90 porting power gains?

decipha

Registered User
anyone have an A / B comparison of a ported early m90 blower compared to a stock blower?

how much more boost does a typical ported early style m90 put out compared to stock?

anyone have any dyno results or 1/4 times they don't mind posting/talking about?

I was playing around on the dyno the other day and my blue 92 5spd completely bone stock put down 200.01rwhp on a dynodynamics at 105 degrees in the dyno room. Only thing I did to it was lean it out from low 10s to 11.5 AFR on the top end, all else is stock.

keep in mind it has a slight head gasket leak and a slight misfire on 2 cylinders, I have to put a gallon of coolant in it a week traveling ~200 miles, and at idle the car stumbles every now and then, its still got the stock 92 plugs and wires :eek:

I know I know I just haven't had the chance to get around to it, only 72k miles on the odo and I have my other supercoupes I drive as well so its not a big priority.

Perhaps with cooler temps in the dyno room and maintenance I could get possibly 210rwhp??

but anyway, anyone know what the average gains are porting an early style, I don't want to take away from what the car is so I want it to be stock appearing, I already have a fast car just one this one to be stock with a little extra ummpf
 
I can tell you just upgrading to a late model blower is a huge difference...So Ill assume some porting will make a difference as well...But unsure it will match the later model blower
 
I went from an early model blower with a 5% pulley to a late model blower with a stock pulley and exhaust. After this, The car picked up a full second, in the quarter mile. Big time difference.
 
I took my stock early model, ported the inlet moderately, smoothed the outlet, coated the rotors, and added a 10% pulley. The boost went from 11 to 14+. This is on an otherwise stock engine.
 
One thing people have to stopped going by is "BOOST" numbers... Boost numbers, with other numbers with it, will really only tell you if your changes have increased efficiency of your motor compared to previous runs in relation to how much air the motor is moving. You keep saying boost went up, but did the air flow go up as well going into the motor???? If not, then whats the point of doing the work except for adding more stress to everything.

For example, with my recent upgrades I am moving exactly the same amount of air (570cfm) but I have dropped over 3 psi of boost.... which means the efficiency of the blower and the motor are up.

Look at your maf voltage and compare it to previous datalogs to see if you are moving more air at similar rpm points. Then look at your LOAD values and see if the pattern of the LOAD graph has changed, ie does it stay up longer over a broader rpm range etc or does it drop sooner, or does it stay exactly the same.

Don't look at the numbers themselves or the maf flow numbers as those are not accurate in the sense that they change everytime you "tweak" the tune. In fact I hardly ever look at maf flow numbers anymore except when I want to do cfm calculations then I "correct" the numbers to bring them in line to reality.

With your blower, datalog before and after numbers and do it alot, and see what changes have occured WITH THE EXACT same amount of OD.

Because of my extensive datalogging (we're talking almost 10 gigs worth of datalogs now) I can tell everyone that more than 15% OD on a late style, properly ported blower really does not net a whole lot unless you have EXTENSIVE porting done and everything else to match.. including a better IC. 20% is the max that blower can do, as after that even alky injection with big mods etc will make less power, but net a whole lot more stress on the motor because of temps that go through the roof. I would venture to guess that the older style blower is the same.

Fraser
 
Along with what Fraser has said, porting the blower will not increase boost or airflow unless you area already spinning the blower to rpms beyond it's usable VE range. In a sense, the best you can do with blower porting (from an airflow standpoint) is restore design intent performance.

Now from the aspect of blower drag and heat generation, that is a different story. You can make useful gains from porting by reducing the amount of heat generated and the associated parasitic losses without increasing OD or boost.
 
Anyone who wants a rotor case to port I've got one for you. 40$ shipped to lower states. No scratches, just needs to be dusted off and all the threads are perfect!


 
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