eldopa69

i think it would be a great reference for everyone..

VAP

and then only if done on the same dyno at the same temperature and even then it's "iffy." A 2lb variation in tire pressure, in only ONE tire betwen 2 consecutive dyno runs can cause a variance of +/- 15HP! And you could count EVERY dyno run at this forum since it's inception on one hand and still have multiple fingers left over.

eldopa69

what about approximate guessstiations based on experience?

VAP

Given those two scenarios then should we consider the modification mentioned perhaps a 7.5HP gain (an average of the 2 perceptions?). Not at all. The truth is it "may" be a 20+HP gain or it could as easily be a 20HP reduction in HP or anywhere in between. When you're compiling any list like you're recommending vague/ambiguous findings do nothing towards any kind of credible answers. All they do is muddy the water further than no list at all.

eldopa69

completing your overhaul, take it to the dyno -n- see if your gut is full of ****e or not.
my gut tells me that the full p-n-p of IM and heads and a meticulously rework of the intake tract is the best and most fuel efficient approach to a cushy state of modified bliss.. according to what ive read, it seems as though i culd bet on having afc exhaust manifolds on my 95 90q. so, im capable of farting out upwards of 400 cfm (polished).. if a meticulous p-n-p is done with intake and ported tb, will 400 cfm be adequate??

thanx

VAP

basis or foundation from which to determine "net gain" if any.

And as far as porting/polishing it's a black art which most people can't even begin to understand. Most think hogging out all the intake/exhaust runners is the direct path to utopia and little could be further from the truth. Without CCing all 12 upper/lower intake runners in the intake manifold, int/exh runners in the heads and EVERY combustion chamber to within 1 drop liquid volume of each other most will actually accomplish little if anything on their first attempt at P&Ping. And there is simply NO other way to insure equal TQ/HP in EVERY cylinder. With EVERY .001" inch removed from any intake runner ID to improve flow an equal or greater loss in velocity "must" be expected. It's the law! And velocity in these heads is crucial. Thats why ITB's can make more power on a normally aspirated car than most any factory intake manifold. It's beacuse of their individual velocitiy speeds at the cylinder that makes them perform like nothing else.

eldopa69

so, one could take hundreds of attemps and dyno runs to achieve IM nirvana.
if you are using the flexhone attachments, perhaps you should run a stopwatch on each runner to ensure that you are getting approx. the same material removal. i have done 12 years of metal fab.,so ive done my share of grinding and polishing. ive never used a flexhone, but i can tell by looking at them that (at a constant speed) they remove material at a consistent rate, thus, the stopwatch thing..

VAP

nor are they identically configured. One flex-hone feels loose in one bore and tight in the next... simply put; there is NO shortcut for CCing, PERIOD!! And flexhones "wear"... they get slightly smaller after each consecutive bore is honed. Then there's the matter of controlling speed when using them as hones spin faster in loose bores and slower in tight bores. And they have to be used with oil. If dissimilar amounts of oil are used inside each bore then dissimilar results are obtained.

quattro90S6

showing actually numbers would not be too easy since the only time i have been on a dyno was when i had done most of my engine mods already and i was getting a misfire. Realized a slit in one of the spark plug wires was grounding out on the IM occasionally, but that was days later. Same with lap times at a track, i have only been to 3 track days ever, 2 at NHIS and one at the Glen, i may have times for NHIS but would have to dig them up, however, there was a fair amount done to the car between those two trips.