RotorJoe

I own an 88 N/A and I am about to do the TB mod and the porting of the manifold. The question is, are the benifits great enough to swap the manifolds. I would also like to port what ever manifold I go with, so if I port the S4 manifold will the increase their be comparable to the porting of an S5 manifold? What would you do if you had the choice?

GLHS

S5 all the way, just make sure the VDI will still work, or its not worth it..And port it out, just leave the primarys alone, I have heard they are large enough now, if you port them you lose alot of velocity..

This is what I was told by a SCCA racer..He may have been full of it?

Rotorific

iTrader: (1)

I like the S5 manifold but i eventually swtiched back to the S4.... It was alot of work to put it on but it was worth it... I could notice how the flow characteristics helped power wise up top... -Gabe

RotorJoe

Does just swapping the manifold over from the S4 to the S5 bump the horse power up to what the stock S5 engines are (160 or so), or are there other differences that push the S5 engines up to 160? How much horse power does just the swap produce on a stock S4 engine? But from what I hear it is worth the trouble to switch to the S5 manifold on the S4 engines. I am pritty sure some has done this, but I can only find the threads that say go for the swap, no details on the parts or what I need to do to make the S5 manifold work. P.S. While I am in there should I go with the PineApple six port sleeves or jost clean my old ones? A link to these threads would work too. Thank You for what ever info you can give.

BDoty311

The 160 S5 power came from the manifold and lighter higher compression rotors. There is a dyno run before and after of the S4 motor with S5 manifold vs S4 manifold floating around here somewhere. You will gain power from swapping it on a stock-port motor, but many believe that the S4 is better for a streetported motor.

pp13bnos

iTrader: (1)

Many people beleive that the s4 is better, but I'm yet to see a dyno sheet. Until then I'll keep on using the shorter intake manifold design of the s5. Keep in mind, i'm talking about the vdi in high mode. CJ

BDoty311

heres the link
https://www.rx7club.com/forum/showth...threadid=95492

RotorJoe

I know I said I was looking for stock numbers which is good to give me a base line hp numbers for this mod. But I should tell you that I have a stage 1 street port. Thanks for the thread link. Please keep um coming, all help/info is much appreciated.

silverrotor

iTrader: (1)

It's been done before. Although some people have found good results, a few have said It's not worth It. You lose more than you gain. Your down 10 horsies, (from what you originally had, prior to s5 Intake swap) ,until you reach 7000rpm! It's from than, that Is when you actually gain a little more from your Initial Intake.

I know of 2 FC owners that highly not recommend doing this. Maybe you'll be a bit luckier. Perhaps they had tired motors.

Last Winter I was going to do the same swap. I had everything ready to go... brand new gaskets, silicon lines and bolts. Polished up and cleaned Internally s5 Intake ready to go until I had someone I trust say..."I wouldn't do It dude". That was enough for me.

silverrotor

iTrader: (1)

Like a faster processing ECU, higher compression Rotors and a 15% reduction In weight of the Flywheel.

rotarygod

iTrader: (1)

The S4 manifold has shorter runners than the S5. The gain the S5 gives is due to VDI. The Renesis also has VDI if that says anything.

I've heard that the S4 manifolds flow better for ported engines. Just by looking at the two side by side I would easily say that the S4 flows better but that damn VDI seems to change the rules. I have an S5 manifold on my GSL-SE but it is also highly modified. The GSL-SE had much smaller throttleplates and intake runners so I'd have gotten a gain either way. Hard for me to compare.

I did the porting as described in the thread but later filled it back in with epoxy. The top end did increase but the mid range suffered from a loss in velocity. Instead I moved the secondary injector location and ground this internal area smooth. I also filled in more of the intake manifold with epoxy than was there stock. On the stock S5, the runners expand in area around the injector holes. Once you remove the injector turbulence you have a decrease in velocity which is why I had to make the runners smaller. I still have the top end that the ported ones have but now I have all the midrange power back that was lacking in the ported one. I also heavily modded the plenum and changed throttlebodies to a single plate. Hmm...I wonder how the RX-8 does it??? Single!

Porting the S4 manifold won't give you any noticably impressive gains. There is absolutely no point (or room) to do the egg shape thing that you can do on the S5. There are little things that can be done but nothing all that fantastic.

silverrotor

iTrader: (1)

I did the porting of the s4 Manifolds, In conjunction with the TB Mod. I ported very very little. I did notice a better response but that was mostly attributed to the TB Mod I think.

*edit* Main point, I forgot to list the VDI attributing to the Increase In hp over the s4. Ironic...