Hatchet Jack

The thread concerning itb's and pcv stuff took an interesting turn towards intakes in general and how to run efficiently. For easier location for other forum surfers, I'm starting this one devoted to intakes specifically. Plus it's fun!

I have a half bridge 6 port with the center iron ported upwards and bridged past the housing. The end plates are nearly stock; just the lower main ports are opened earlier, and the aux ports are stock with inserts. My itb intake manifold, like most all the rest on the market, combines both (all) ports of each rotor into one runner. This is where I need advice.

I could go to the stock S4 intake setup, giving less vacuum through the bridges, and more vacuum to the secondaries to have brakes again. However, I've read the S4 intakes cannot flow enough for much over 200whp, but I've also read half bridges hardly make over 200whp regardless the intake. The runner length for the bridged primaries would be all sorts of messed up, but the secondaries might be ok.

Or

I could buy a 4 barrel intake with a progressive 4150 style throttle body which would have the same capabilities as the S4 intake only with lots more flow and lots more money. I got the part$ in the web cart, but I'm reluctant pulling the trigger. $$$

Or

I could keep what I have if you think I'm splitting hairs.

What do you think of my situation, and what's your setup?

Hatchet Jack

Just in case anyone's following or is curious down the road, I'm leaning towards the stock S4 intake or keeping the itb's i have. There are definitely areas to be ported in the S4 runners. I also think taking out the 5/6 port actuator rods would help with flow as well. It just doesn't seem that my itb's in my particular situation are very beneficial, and I'm uneasy spending the money on a 4bbl tb setup. I'll post pics when stuff actually happens, though.

Hatchet Jack

Did a little math according to this ancient thread (Here's how to figure out intake runner length - RX7Club.com). Not sure if that thread bears much weight anymore, but a fascinating read nonetheless. This is the S4 intake on my engine.

Primary runners theoretical peak hp - 3706rpm @ 2 RV, 7412rpm @ 1 RV
Secondary " " " " - 6119rpm.

Ad this to other S4 intake info I've scrounged up, and I'm not encouraged.

j9fd3s

iTrader: (3)

if you skip to the end of that thread there is a disclaimer that the maths are incorrect.

that being said i don't think the S4 manifold would work very well, a port with a lot of overlap will not want a plenum, and the S4 has a plenum on the primaries. it also doesn't move enough air

Hatchet Jack

Thanks for the advice! I'm down to either making an airbox for my itb's or just going the 4bbl tb route.

j9fd3s

iTrader: (3)

https://www.rx7club.com/1st-generati...irbox-1074310/

Hatchet Jack

That looks beautiful. I wish so bad that would work, but I have throttle bodies from an Arctic Cat snowmobile, and their layout is not very conducive to an airbox. This is my dilemma.

ibeljin

iTrader: (1)

A member way back made an intake manifold which uses the stock TB and is basically a straight shoot right into the keg. heres some more info on that and the second link is what it actually looked like. I believe the rx8 had different runner length for primary, secondary, and auxiliary ports, might be worthwhile to have a look at the possibility of multiple length geometry with the use of ITBs.
https://www.rx7club.com/time-slips-d...inside-416012/
https://www.rx7club.com/2nd-generati...-s5-na-834592/

Hatchet Jack

I finally made an airbox. It was my first time messing with fiberglass, so it's super rough, but it should be good enough. Since I already mutilated my hood for my old sock filters, I'll need to cut it up a little more and make some sort of scoop to clear the airbox. In the next week or two, I should have an update on whether or not it made a difference compared to the oiled sock filters.

Pettersen

iTrader: (1)

I like it! Refreshing to see something other than a pod filter.

ibeljin

iTrader: (1)

is that a stock sized airfilter? really interested to see if there is a measurable performance change when using stock filter elements

Hatchet Jack

Yep, stock K&N. I considered the size, but just went with it anyways since I already had it. I can always run no filter to see if it wants much more fuel, but I can't imagine this little piglet wanting more air than this filter will allow.

Hatchet Jack

I can't draw too many conclusions yet, given everything always seemed too rich one day, then too lean another; maybe just the nature of Alpha N? Anyways, today everything seemed rich. Before wot was around 12.5-13.2:1 all the way. Today it was ~12.5:1 in the lower rpm's, but 7k on up to 8.3k was 11.9:1. I didn't try it with no filter to get a base, though.

The intake temps are definitely better: 55* outside temp before - >110*. 55* outside temp now - 75*

Not sure what to think yet.

j9fd3s

iTrader: (3)

what ecu are you running? it probably needs some work on the baro and or air temp maps.

Hatchet Jack

Megasquirt 2. I'll confess, I'm not a great tuner. My tune is very gradually becoming better, but it wasn't hard to improve from where I started.

Hatchet Jack

I thought alpha n used just rpm and tps. I definitely neglected messing with the baro and mat correction tables, but it looks like those are for speed density algorithms. If not, I have no clue how to adjust them!

Edit: Found this on the Mega Manual Tuning Your MegaSquirt

Oops. Looks like I'm supposed to tinker with those maps, too.