deep thoughts on VE

Dusterbd13 wrote: hmm..... y'all are making me ponder a full 1 point increase in compression. maybe a .5 increase whould be the better bet, as im am unable to tune the ECU in this car, and must retain it for NC inspection. i could go megasquirt, but again, inspection,autocross classing , etc.

What auto-x classing are you looking at? Much of what I'm reading here would put you into Street Mod or Prepared. Port-matching is allowed in Street Prepared, but it's limited. The are limits to what you can do to the cylinders and heads as well. (see page 105 of the current rules).

Otherwise, fun thread to read.

i figured that the ms or whatot would kick me up to running with the stuff like tube framed cars. dont want to be completely outclassed...

i really am not building for any particular ruleset, but i am using street tire classes as my general prep level. that looks like where id fit in best. my duster is classed cp, so i already have one very non competative car.....

In reply to Dusterbd13:

Then realize any sort of porting isn't really allowed at all in the Street Tire classes. Google Andy Hollis' article about building a Civic ST engine. While the details are specific to a Honda, it is a great overview of what you can do within ST rules.

Unless you don't really care, then whatever... I have some friends who run Spitfires in FSP with engines that are totally illegal, but they are still so outclassed by a well prepped Honda nobody cares. Especially at the local level. Comparing times, I could prep my TDi wagon for FSP and probably be faster.

I can't speak to others theories.... but in my case... the reality is improved efficiency. Check EPA figures for yourself...

If you are competing... those who write the rules....

In my case Grunts original lump was making all kinds of weird noises... so a new lump was in order... so it made sense to do a few efficiency improvements while I was rebuilding her replacement...

Here is another improvement in efficiency... the intake side of Grunts head... before and after. Note the keystone shape of the original splitter has been blended away

so heres where im at with the intake, pre cleaning. have not really started on the "polishing" yet. this is all just cutter work.

does anyone have advice on the turtles? i shortened and shaped the first one a litle bit. its about equal height to the second (from the throttle body), instead of the origonal much taller.

how about the divider wall in the middle of the plenum? lines up with the one port dividser in the upper intake, so i didnt want to just cut it out. but all is seems to do is block air form 3/4 runners.

so, anything im missing? any further tips? anything you see that i should address before finishing up?

Hmmm, Not familiar with the overall intakes shape... can you take a few photos showing assembly as a complete unit?

Your tool control is quite good(from what I see of the radius's)

Don't remove too much of the "turtles", They appear to be located to help direct airflow to the ports closest to the T/B intake

REMEMBER flow direction... it is VERY hard to make a perfect manifold to port match - keep port edges out of the airstream (DON'T overport the manifold flange.... it is far better to have the head/port opening a little larger, then to have the manifold/port mating point opening a little larger.

Additionally - Recommend you purchase a SPARE cylinder head. Do some research into the head... find everything you can... Valves/seats/bowls contribute a great deal to improved efficiency.

oldeskewltoy wrote: Your tool control is quite good

i guess its been too long of a day. that made me giggle......

and i try to have a steady hand. my hands will start to shake for no apparent reason (other than low blood sugar....) so i stop then. all i know about doin this kind of stuff, i learned from doing woodworking. i love my 1939 craftsman 34 inch lathe......

i did not open any of the ports at the head. stock size. just cleaned up, with the humps under the injectors ground down. i only marginally cleaned up the plenum side, and re-radiused the transition from plenum roof to runner, as it was a HORRIBLE angle.

the turtles are there to direct air. but the first one was so big it covered 1/4 of the opening to the throttle body. just huge,. dwarfed the second one. so i smaller-d it.

thanks for the kudos. i started smoothing this morning before i left for work. just using an 80grit flap wheel on my drill is making pretty quick work of what i can get to. then its on to the tootsie rolls, little drums, etc.

and i ded get a spare head. traded for it last week. that way, i can build it, and do a one day drop and swap. this car IS my daily,.....

check the acr build thread and youll see a picture.

michael

Dusterbd13 wrote: hmm..... y'all are making me ponder a full 1 point increase in compression. maybe a .5 increase whould be the better bet, as im am unable to tune the ECU in this car, and must retain it for NC inspection. i could go megasquirt, but again, inspection, autocross classing, etc. this is the kind of discussion i love. mnakes me do lots of research to learn more, and expand my knowledge basis. ill be doing that on combustion chamber effeciency vs spark lead tonight, with a little bit of boundary layer theory thrown in. so, now that im rethinking compression, in also rething header/exhaust. what ive always been told is that the scavenging effects of a longtube are much greater than the effects of a short tube, which are only slightly better than a stock manifold. after looking at stock manifolds for this particular engine, i cant see how a short tube is not a major improvement. with the short tube, the primaries are not the same length, or even anywhere close. the transition into the collector is also a jumbled mess looking at it. with the long tubes, the collector design is much better, the primaries are almost the exact same length, and the air is a much smoother, easier flowing path. but from what i understand, the SHIORTER primaries produce more low end rpm range, while the longer favor higher rpm. i know a lot of this depends on diameter of the primaries as well, but so far i have been unable to locate the data on ID of the headers. we are assuming OBX ebay pieces for this, as they are the most cost effective solution. the other alternative is to use a stock exhaust maifold that has been ported. this has more equal length runners than the short tube eader, but of an unkown ID, unknown consistency, very poor merge at the collector, and very necked down. i could port match it, and open up the neck a little bit, but again, were working with variables insode the runners that i cannot see or do anything about. but externally, theres quite a lot of variance, ut like 1/2 inch or so. after this comes the exhaust factory gave me a mandrel bent 2.25 id exhaust, with a ok flowing muffler. i have a 2.5 inch mandrel bent pipe, and could end that with a single inlet, single outlet dynomax super turbo muffler. this would be freer flowing than the factory, sound pretty nice, look a lot better. but would the increase in diameter, and therefore decrease in velocity, move the effectove RPM range highr again? again, most of my driving is in the 2k-4k range on the street. ill wail this thing the whole way to the rev limiter on track, and on the street on occasion. thats 7400rpm. but where id like my gains to be centered upon is the 2k-4k range. broader would be better, like 2k-6k, but i believe that to get the gains at 6k, id be loosing more than i gain at 2.5k does this sound right?

so im back at this again. reason being, the current motor in the ACR is using oil and its time for a fresh one. the head was bowl blended and the chambers cleaned up. just a good cleanup like i did on the intake.

i still have to decide on exhaust, compression, etc. car will not be a specific autocross class, but must retain stock ECM for NC emissions.

basically, were looking at stock bottom end, stock cams, mild porting on head and intake, 52mm throttle body. very minor modded engine.

if y'all can continue this discussion about compression and exhaust for the VE side of things, focusing on the 2-4k range, id greatly appreciate it.

michael

i've logged my new mazda skyactiv engine hitting VE's over 120%.

oldeskewltoy wrote: REMEMBER flow direction... it is VERY hard to make a perfect manifold to port match - keep port edges out of the airstream (DON'T overport the manifold flange.... it is far better to have the head/port opening a little larger, then to have the manifold/port mating point opening a little larger.

I'll have to keep this in mind when building an ITB adapter.