mark kibort

This point is VERY disputable. (not that cooling air doesnt provide hp, but doing it this way on the 928 would do anything) You have a huge oven right below the intake and it will tranfer heat very easily to the intake "U" after the throttle body.

The air transient time is very short and the surface area that it is in contact is relatively short. ever wonder why intercoolers have all those squiggly paths? Its to provide time and surface area for the heat to be disappated. Sure, there is still going to be heat transfer with any kind of spacers. the question is the difference in temp of the intake charge. It will be ever so slight, both in temp change of the air at WOT and 5000rpm, and in intake plennum temp. there is no hidden HP gains lurking here, and more potential issues as Carl has pointed out. Again, at the race track where you are WOT more than half the time, pull into the pits and the intake plennum is almost cool to the touch, showing that the mass of air flowing through the intake is cooling it. More importantly, you have the heated plennum due to the engine heat where there is no air flow and that is like an oven that cooks the intake .

Its not like the american (or other) cars designs, where the intake is physically spaced from the engine and you are thermally disconnecting it via the plastic spacers. The formula for what HP gains you will make for a tempurature change tells us that any net change that you could expect, woud be minimal. well designed turbo intercoolers take 100s of degrees out of the air charge. Now, that makes huge differences in more than one area!

mk

Niklas Kampe

We did before-and-after testing with similar spacers on a supercharged S4 some months ago. The testing wasn't done on a dyno, but rather we data logged boost and MAF signals and made calculations based on that. We concluded the power gain was around 1%.

Note that since we did not do a proper dyno measurement, these results may not be that accurate. Also, a normally aspirated engine may be a very different story.

mark kibort

I think using those indicators would be a stretch to make anything out of the results. too many variables that are not taken into effect. im sure there could be 10% variance for two supercharged cars with similar boost and MAF signals

Only way to do this one is on the dyno!

Mk

soupcan

Back in my Drag Racing days we machined a set of phenolic spacers for a 452 Chrysler engine. We made them to replace the aluminum intake spaces required when using Stage VI heads. Made no difference at all as compared to the aluminum spacers, the 1.5 inch phenolic spacer for the carburetor did make about .05 difference (as compared to the aluminum spacer) but that's from keeping the carburetor bowls cooler. Not an issue we have.

IcemanG17

Carl
If you want I can put a set on my track shark, which is a stock internal 5.0L S4 with full race headers and exhaust...right now at 304whp-291 torque.....the bummer is the intake is a not too pretty

OR I could put them on my bone stock 88S4 automatic which is VERY pretty...

Carl Fausett

An excellent point! I like your idea of the button-head fastener too. I bet a fella could get the covers back on with those. Thanks for your input.

dprantl

I'm really interested to see what the dyno differences will be, specifically with forced-induction. I'm pretty sure there will be some gains with NA cars, but not so sure about boosted ones. Then again, those trumpets are so damn close to the wall when stock, there will probably be gains no matter what the engine is doing.

Dan
'91 928GT S/C 475hp/460lb.ft

Carl Fausett

One school of thought is that the process of supercharging tends to over-power restrictions in the engine, and that is why gains like exhaust system upgrades are smaller on SC cars than on NA cars.

But physics and fluid dynamics tell us that the gain on a boosted engine should be exponential to the boosted air flow - so therfore the improvement should be even greater on SC cars than NA cars.

Bottom line - I want to document what happens in the real world also.

Bill Ball

Yep, that's needed. Whoever does this, look at area under the curve as well as the peak numbers. I tried some sidecover/throttle mods to my car with Tom Cloutier about 5 years ago when my car was NA. There was no change in peak HP but there appeared to be some benefit in the mid-range RPMs. Brian has a couple of good test mules.

90 S-4

Carl,
First, thanks for bringing another product to the 928 crowd.
But, If you really wanted an as close to perfect test as possible,
wouldn't it be more accurate to measure your own car with and
without the blower hooked up. You should do it on the dyno, same
day, same car, same dyno, same dyno operator, same temperature,
same tension on the tie down strap, & FWIW all the research I've
done shows that the spacers mainly help the stroker motors, but I'm
very curious to see what you come up with. Thanks for taking on the project.

Carl Fausett

Valid points, Joe. But my 928 is behind 2 feet of snow at the moment and I didn't think you guys would want to wait until spring to find out. I have had two solid test mule offers so far from sunny climates. This will get us a unbiased result a lot faster.

Carl Fausett

Sterling: were you ever able to quantify the improvement the spacers made on your stroker motor?

Z

As some of you know, Todd up in Green Bay has a wideband O2 sensor for each cylinder, and also has an aftermarket engine management system with sequential fuel injection. He can see how much fuel is going to each cylinder, and what the air/fuel ratio is for each cylinder, so can tell how much air is going into each cylinder. If you look at the engine pictures in the post linked to below, you might notice something.

https://rennlist.com/forums/5633781-post1.html

90 S-4

only one on the driver side

Lance J

anything like this for OB's????? i have a bone stock 79