Intake Filter/Terminal Velocity Test

[Great Boob]

I followed the thread last week on the KN filter deal, thought I'd try a crude test. On my '84 sedan, 250k + well maintained miles. Uncorked the turbo by removing the entire intake assy., found a straight stretch of highway and ran WFO for several miles, slight upgrade, top speed 108 - 109 mph.

Replaced the whole intake assy.,, with new filter, ran again on ther same streath, top speed approx. the same.

What does this tell me? Not much really, I mean top speed is probably more dependant on rear end gearing than anything else. Also, I expected the turbo to emit a cool whine. Instead, it sounds lake an industrial weed eater with an attitude! Think I'll leave well enough alone.

[pberku]

Originally Posted by Great Boob

.....Think I'll leave well enough alone.

Smart move. If it ain't broke don't fix it.

Phil

[t walgamuth]

i think it proves that your stock intake is not an impediment to top speed. which doesn't surprise me.

tom w

[Johnhef]

Originally Posted by pberku

Smart move. If it ain't broke don't fix it.

Phil

If it ain't broke, fix it till it is.
I've got the cheaper ebay kit on mine, what junk. If I could only remember where I put my stock intake bracket and box i'd be back in business.

[SD300]

Filter or not will not change your terminal velocity, but less air restriction will help your acceleration.
Stock air filter can't be all that bad, may not be the best, if they can design the whole car, the engineer can't be that dumb.

U need so much surface area to allow so much air cubic foot per min to pass thru.

[t walgamuth]

wondering how it could affect acceleration and not top end? top end must require the max power. why would acceleration be affected differently?

tom w

[boneheaddoctor]

Originally Posted by t walgamuth

wondering how it could affect acceleration and not top end? top end must require the max power. why would acceleration be affected differently?

tom w

lower restriction = quicker spoolup = faster acceleration....

even if the higher restriction filter provided enough air to reach max power, the lower restriction would edge it on the spoolup issue and therefoire the acceleration...

But its splitting hairs in all actuality...these cars aren't that quick and a 1/2 second faster acceleration really isn't going to matter a hill of beans.

[t walgamuth]

to see any evidence of lower restriction.

i think that the k&n is a good product, high quality i mean, and it works for many cars which are limited by air cleaner size. i am not convinced that the mb is air cleaner restricted. the test above in first post is good evidence of it.

tom w

I have to wonder if the (small) advantage of these aftermarket air cleaners is offset by relocating the air intake to the engine compartment. The stock air cleaner has a cold air inlet. Most of the aftermarket setups I've seen have a K&N type filter installed near the turbo. The air in that area must be 20 F hotter than ambient. I suspect the temperature effect is greater than the pressure drop effect. I also find it hard to believe that the inlet pressure drop would affect the turbo spin-up time significantly. I would expect the rotating inertia of the turbo to be the limiting factor. Just my opinion.

[boneheaddoctor]

Originally Posted by t walgamuth

to see any evidence of lower restriction.

i think that the k&n is a good product, high quality i mean, and it works for many cars which are limited by air cleaner size. i am not convinced that the mb is air cleaner restricted. the test above in first post is good evidence of it.

tom w

That was top speed.....all that proves is the engine got enough air...

but that can still be enough to slow spoolup a bit...and acceleration...

But without some sensitve instruments to measure .......the butt dyno isn't accurate enough.

THe turbo does spool at a lower RPM with the aftermarket airfilter setup...

but like I said...that helps drivability a little...but differences are not dramatic..and arguing the point is like splitting hairs...

just like arguing if Delo 400 oil is better than Mobil one.