rx-7fc

i just put a 89-91 intake manifold and i an thinking about putting my old intake manifold back on my 86 because people say if you don't get the vdi working you will lose hp and right now i don't have it working i just have it wired open and are there any things that i should know about the 89-91 manifold or put the old one back one

scathcart

Any engine mods? specifically, porting? I can't decide until then.

rx-7fc

mods:racing beat headers road race,K&N air filter,tbmod,
one high flow cat but thinking of taking it out,msd spark plug wires 8.5,no a/c,no acv.

rx-7fc

and how do you put in a RPM switch from summitracing to get the vdi to work

scathcart

no catback, intake manifold porting, or engine porting? 89-91 intake would be better.
I'll get back to you on the VDI actuation. I am not as good with S5 NA cars as I am with Turbo cars, but I was under the impression the VDI opened from pressure. Well, what you could do is plumb the vacuum line into your air pump (and also use the air pump to actuate the auxilary ports), and then use an emission solenoid of a parts car and the rpm switch to activate it.

The RPM switch simply wires into your ignition system to read spark, and then sends out a 12V signal whenever the rpm determined by the "pill" is reached. This 12V signal would open the soleoind and allow the pressure to open the VDI.

I'll read my FSM and get back to your with any more info I can come up with.
Sean Cathcart

rx-7fc

i can do porting on the intake manifold because i have to take it off because of a vacuum leak and i don't know if it has a catback

rx-7fc

bump

avrfan

why did you put the newer intake on anyways? Did someone tell you that they were better? I know the 90-92 engines are better because of higher compression and lighter rotors/flywheel(more power & performance) but just putting the intake from a 90 onto an older 13b is not guarantee to get the same performance. The intake does look different but I have no idea if it really is better or not.

dav

rx-7fc

bump

blu_gxl

yes it will give better performance some people have done the swap and all say they have gotten a gain. i believe though you won't realize the ful gain unless you have the vdi working or wired open like he has, some people wire the vdi open i don't know why for sure but i'm guessing it's because the stop functioning properly.
also there is a write up some where on how to do the swap and rpm activation via the switch i'll see if i can find it
here it is http://homepage.mac.com/carldavis/intake/intro.html
enjoy

james

dre_2ooo

If you feel a kick at 5.5k, it's working.

Get a ported 89-91 intake with free flowing exhaust. Will probably gain you 25-30+ hp from the stock 146.

mazdaspeed7

Where did you hear that? I have seen a few dynos of S4's before and after putting on an S5 manifold. The results? 10-11 RWHP every time, no porting or anything. Just wsapping out the manifolds. Not to mention the extended powerband from the variable runners. Compression only accounts for 4% increase in hp for every point the compression is raised. Mazda raised the compression from 9.4 to 9.7 in the n/a's. That accounts for 2.3 hp of the 14 hp increase from 88 to 89. The lighter rotors might make another hp or two. But the biggest factor int he power bump was the intake manifold.

Putting an S5 manifold on an S4 is definately worth it. Not only does it add a dyno proven 10 rwhp, it also extends the powerband. And thats without porting. Porting the S5 manifolds makes a HUGE difference. Just ask PP13bnos or dre 2000.

silverrotor

iTrader: (1)

A fellow RX-7 owner had done the same conversion on his 86'. He claimed that-yes you do gain 8-10 hp, but thats only at 7000rpm. Also, even before 4000rpm, he had actually lost 10hp. His dyno sheet speaks for Itself. He had the VDI hooked up to an RPM Switch and also mods to his Intake and exhaust were done. But that Is besides the point.

Quite simply, power gains are their, but after 7000rpm and a lose of power below 4000 rpm are lost. He had the exact same write up as what blue gxl has. Many RX-7 owners have bee disappointed of the Series V Intake swap, so they re-converted.

I hope this helps!

rx-7fc

i might think about porting the manifold sice it is out the car right now