1st_gen_rx7

I was wandering if I could use a turbo intake for a n/a setup. Currently the setup is a S5 13b turbo block with S4 N/A rotors, half bridgeport with a racing beat Holley carb. I have a few reasons of wanting to switch up, one is an ecu would also help with my ignition upgrade. the other is I absolutely hate the corner bog of the Holley. My concern is the throttle body not flowing enough CFM or being restrictive. I plan on using a mega squirt kit to run the fuel and ignition.

diabolical1

iTrader: (3)

I think Peejay (years ago) had posted a fairly thorough explanation as for why it's not a good idea. At the moment, I can't remember if it was a theoretical explanation or something he had figured through testing his own stuff, but either way I remember him posting about it.

That said, can it be done? Of course. However - and I'm not trying to overstep here - but, if you're going Megasquirt, then why don't you look into one of those Holley-type throttle bodies? It may not work out, but I think it's worth a look.

1st_gen_rx7

Mostly looking into it because I already have everything. Just throwing the idea around, looking for reasons not to.

1st_gen_rx7

Mostly looking into it because I already have everything. Just throwing the idea around, looking for reasons not to. Can I buy just a throttle body from Holley?

TonyD89

iTrader: (10)

You most certainly can just get a throttle body from Holley or Edelbrock. They come with fuel injector placement or, as has been said on the forum before, just run large enough injectors in the center plate to and no need for secondaries. I think it was Blue TII that said the cheapest way to get to fuel injection is is the aftermarket Holley four barrel manifold, holley or Edelbrock four barrel throttle body, and sufficient injectors in the primary position in the center plate, don't worry about secondaries and staging.

1st_gen_rx7

For the cost of the holley fi I may go a different route. Maybe a 48 ida with a better igntition setup.just to keep it simple.

Lavitzlegend

iTrader: (3)

Why not just gut the Holley carb you have now of all the fuel components and essentially use it like a throttle body, place 2 ID1000 injectors in the primary injector holes, wire up a megasquirt and go? I have an S5 T2 intake on my full bridge n/a setup and I will most definitely be switching to an ITB setup relatively soon. The T2 intake is just too long and not optimized for n/a performance/harmonics. Just my 0.02

edit: I also have a T2 keg but running a full bridge and s5 n/a rotors. Running PowerFC right now but will also be switching to MS3 Pro Evo with 2x ID1000 injectors soon.

diabolical1

iTrader: (3)

I was actually going to suggest this as well. That, or get a broken one of decent size and do it to that one.

BLUE TII

iTrader: (9)

I thought Peejay found the TII intakes weren't good when modified for the 6 port NA motors.

I know the TII intake manifolds work well NA on the 4 port turbo engines when run NA on street ports, but I don't know about half bridge ports.

There have been a couple of street ported NA TII engines that have dynoed around 210 to 220 rear wheel horsepower with the a ported stock TII intake manifold.
One was Yaw Power way way back and then the other was Defined somewhat more recently.

If you can get a $200 JW Holley 4150 style intake manifold, $150 injectorless TB, $150 carb hat and a set of EV14 injectors over 1,000cc for the primary position and some sensors that would be the way to go.

diabolical1

iTrader: (3)

It very well may have been that. I just remember that someone that I tend to listen to had posted a fairly clear explanation of why the T2 intake was not a great idea on an NA bridge (the runners and plenum). I have tendency to try to store posts in my head for references, but I could have "remembered" the wrong person this time.


EDIT: This does not contain the post I think I remembered, but it does contain Peejay mentioning his experiences with the manifolds on his bridge.
https://www.rx7club.com/naturally-as...-port-1083273/

That said, again, the setup works.
https://www.rx7club.com/naturally-as...-951173/page3/

1st_gen_rx7

Thanks for all the replies. The holley ideas are great, but extra $$$. The only reason I really wanted to try it was because I already have it, minus the ecu. I may save the intake for another non n/a project. One thing I did learn is bridgeported engines make things a little more complex. But would a longer intake help on the low end? It seems it would help make a bp more street friendly. I see 12a bridge ports with long runner 48dcoe setups all the time, granted they dont have the intake chamber.

Lavitzlegend

iTrader: (3)

I bought the exact setup from Jorx7 a few years ago. Installed it in my '86 GXL and it has been fun but definitely feels a bit choked on the top end out on track. I'm hoping to unleash the full potential soon with some Ducati ITBs I bought and a MS3 Pro Evo ECU with ID1000 injectors and FFE trigger kit with LS2 coils. It could also use a better header than the racing beat one I have on it now. Now if only I could stop spending money on the 10AE I bought and focus back on the full bridge...

Dak

Unless there's a TII build I can't find searching. The Defined Autoworks was a 13B-RE block and manifolds. He hit 230rwhp in the end after somehow changing the runner length of the manifold.

BLUE TII

iTrader: (9)

Oh, I had forgotten the base for the Defined 230rwhp one was 13B-RE. Talk about an engine with good intake and poor exhaust potential for an NA build.

The S5 TII from Yawpower many years ago.

My memory is mild street port intake ports, full race exhaust ports, ported S5 TII intake manifolds/throttle body.

I would think a half bridge should be able to do at least that and maybe more if the exhaust port is big enough and the exhaust system isn't too restrictive or mismatched.

peejay

I thought what Peejay found was that a 6 port intake modified to port-match to a TII block made more power at every RPM, AND extended the usable RPM by over a thousand. Drag testing a half bridge Turbo II block (with 9.4 rotors) had best shiftpoints at around 8000rpm with the TII manifold, over 9000 with the N/A manifold. And much better trap speeds and quicker times. It has been a long time but if I recall correctly, my entry to the 100mph club, and my first 13 second time, were with the N/A manifold. Never got close with the TII junk.

The TII intake manifold is not your friend. It is highly compromised to allow for turbo clearance. Consider that a Turbo II had much better port timing than a 6 port, yet it needed a whole lot of boost to only make 40 or so more horsepower. That is pathetic, is what it is.

I have never run a TII manifold on a 6 port block. The TII manifold is compromised flow-wise and port matching it to mate up to a 6 port engine would compromise it even further. You cannot diffuse and turn at the same time!


The Holley manifold is much better than either one for power production. Given the choice, I'd run one of those. (Oh wait, i DO. Er, Peejay DOES) Since I destroyed my last set of good 4 port side housings in a severe overrev incident, I'm throwing a 6 port in my car because it's that or nothing. I'm still paying off the engine rebuild (before the overrev) and the 9" rebuild (and also the build...) and then the trans in my Volvo just puked and that's been another $1500 or so this past couple weeks, so I'm in full gopnik mode right now. But I do at least have a Pro-Jay manifold for a 6 port that is going on there.

BLUE TII

iTrader: (9)

1st_gen_rx7

Thank you, I guess I will keep my setup for now. All the FI kits are really expensive. I may look into a webber IDA setup and experament with it.

peejay

Patience is cheap, though.

I got my 4 port Holley manifold for $100 on eBay because he didnt' quite know what he had. I got my Pro-Jay manifold from someone a few states away for $350 and it came as part of a large lot of parts that the guy just wanted out of his garage (new in Mazda shipping box GSL-SE oil pan, new in wrapper Racing Beat 13B-to-12A adaptor mount and pan baffle plate, a kinda junk Holley 750 carb, a complete tip-to-tail RB single exhaust for a GSL-SE, a tall radiator with fan, an A/C condensor, complete set of new RB lowering springs, and some shocks/strut cartridges still in the packaging and I don't even know what brand they are. Tokico maybe?)

It's only expensive when you're in a hurry to get things done. If you are patient, you can save. I spent a few years acquiring parts for my 4 port 13B, I spent three years building the 9" rear.

diabolical1

iTrader: (3)

Truer words have not been spoken ... or written, I guess.

TonyD89

iTrader: (10)

Was this an S4 or S5 NA intake? Did you just use just the lower part or the entire NA stock manifold?

peejay

S4 N/A. I do not believe the S5 is good for power production because of how much excess surface area it has.

All I did to it was modify the lower. The aux port area was completely filled in, then a TII gasket was traced over the flange and ported in/blended into the port. You cannot do a 100% match at the secondary ports without porting into air, but you can get good enough. Some mismatch from manifold to engine is a good thing, anyway.

I also completely removed the sleeve shafts, sawed off the external dongles, and spent a lot more time with epoxy filling that mess in to some semblance of not having massive amounts of cross sectional area change.

You also need to do something to cover up the ACV port in the TII intermediate housing. A couple of self-tapping screws in the bottom of the manifold to anchor some Quiksteel in the area, and then filed flat after a couple days of drying.

BLUE TII

iTrader: (9)

I'm going to assume peejay means a step fitment with the smaller diameter intake part flowing into the larger intake part is good as it negates chances of misalignment of parts which would cause the converse step situation (bad for flow) and can negate reversion as well
I'm sure he will correct me if I am wrong (in 3rd person like a a true Jedi master if we are lucky).

I recently did a light clean-up port on my 13B-REW tb/intake.
To make it easy I just cleaned up the outside (long) radius of the turns and evened out the lip of the intake flange to the gasket on the flowed from parts and then matched the flowed into parts to the gasket (slightly larger). I used sections of 11/32 x 0.014" brass tube to hold the gasket to the correct spot on the intake mating surfaces while tracing the gasket. Then I cut short sections of the brass tube and loctite-ed them over the M8 studs on the intake manifold to take up the slop when the gasket and intake parts fit together so they will more precisely align.

Much faster and probably 95% of the same effect as the much more intense porting, match porting, polishing and pinning I did on my TII intake way back when- with less downside (larger diameter and too smooth runners needing throttle pump fuel enrichment).

peejay

Nah, you got it. About .060" (1.5mm) all the way around is good.

TonyD89

iTrader: (10)

Thanks!

fidelity101

iTrader: (11)

be careful when smoothing out the ports on the NA intake manifold as inboard the casting is weak and you will punch into the ACV cavity ask me how I know.