Engine Specs:
•old school 4 port R5 13B with Y plates
•9.2 compression ratio (old heavy rotors and 3mm apex seals)
•stock intake port timing with some casting flash removal
•exhaust ports open at T2 spec and close at 12AT spec
•Hitachi channeld "NO" intake manifold redrilled for Nikki stud pattern
•boost prepped 84-85 Nikki (Sterling may have said these are the best choice for boost?)

Turbo:
•Stock S5 turbo with wastegate mod to open further
•May keep water cooling but depends on complexity (I know you can run without on these for a while)

Goals:
•not looking for big power, just better low end torque (that's why I went with stock ports instead of "74 spec" or streetports)
•cool running
•needs to be quiet with only one big 2.5" muffler as there is no room for anything else

The old setup was TOOOOO LOUDDDDDD!








Way too loud for the street. I had to add a supertrapp tip which killed all power (not pictured).

This exhaust got cut up and used elsewhere. The little hotdog glasspack was throw away. I sincerly don't want to build another loud 2" exhaust, but I've got enough parts to do so again including two big Rotary Engineering glasspacks this time. Who knows, it might work out ok, but why take a chance when I have access to an S5 turbo?

So now I need to ask for advice. Should I go through with the S5 turbo? Is it a good idea? I know they're fully divided so they end up louder, but they have better spool down low because of it.

My new exhaust idea will have it exit from the turbo through a 16 or 14 gauge 180 degree u-bend. Then into a Magnaflow 5x8 oval with center/offset core, then terminate under the tubular bumper (push bar) in the same place as the old exhaust. Or close to it.

Will one muffler be enough? Should the u-bend be 3" or can I use 2.5"?

 

oh with turbo + big muffler it'll be quieter than that!

 

So how about a 3" u-bend to act like a 3" downpipe, since these turbos love that sort of thing, then contract it down to 2.5" right before the muffler?

I have to believe a 2.5" muffler would quiet better than a 3", at the cost of some flow at high RPM. Or would it hurt spool more?

 

Next questions. What if I went aftermarket turbo? What size would I want? T-60? GT35? P-trim?

Gotta have good low end/quick spool but don't really need much past 7k. Intake/exhaust port timing is roughly S4 T2. Thanks.

 

60-1 or a BNR modifed stock turbo would do well.

 

its hard to beat the S5 hotside and a Vtrim cold side....

 

Wow, so a stock S5 turbo with a different cold side would be the way to go? Awesome! And I'll pass the info on the 60-1 on to my friend whose baja I'm currently turboing. He's got a 60 cold side but a T3 hotside from a Honduh that he had lying around. It will spool fast but run out way early. The A/R is .48 or something.

 

I ordered this. http://www.cbperformance.com/catalog.asp?ProductID=1451

Billet Fuel Tank Outlet Tee

Makes going turbo or EFI a breeze on a bug with a stock tank.

 

I recieved the part. It looks well made. Uses an o-ring to seal down inside against the bottom of the tank fitting. Now I can go turbo if I choose to.

 

With just a s5 turbo on there no exhaust at idle the car will be quieter than a non turbo with a full exhaust.

In terms of noise control I have good results from

3" inlet / outlet 22" x 10" x 8" drum mufflers which are offset in centre out.

Fit the biggest muffler you can, even if you do a 2.5" system use a massive muffler.

With such limited space I would do a 2.5" system, with the biggest centre offset muffler that will fit in the space you have.

Don't worry about the wastegate modification it won't get you anywhere.

I don't watercool my FC turbo. I never watercooled it. Then when I had a new FC turbo built I changed over to a non watercooled centre housing.

 

Thanks for the info. Sounds like you want to see a turbo rotary baja.

 

Looks like a 14" Magnaflow 4x9 oval with center/offset 2.5" core will fit. Anything longer would not fit very well. Also turns out my previous NA exhaust won't fit now that I've had a brace installed to stablize the horns to the rear deck. So, only enough room for a turbo and one medium size muffler now.

I kinda wanted to go 5x11 oval at 22" long but that won't fit. Maybe a 5x8 oval would fit if it's not too long, but I like the 4x9 as it is wide and skinny in all the right places. Maybe an 18" would be better but I've got this 14" here so I'll try it first. I wonder if I should go offset/offset if I do get a different muffler for this?

Hey, should I get a walbro 255 or something cheaper?

 

Do you think you could fit a same side inlet/outlet muffler next to the oilpan under the spark plugs. Like: http://www.magnaflow.com/02product/s...=main&id=10093
If so, you could run a presilencer to it and get reasonable muffling.

 

That's not a half bad idea. Well it would need to be on the intake/exhaust side of the engine, but not a bad idea.

The shell is only 14" long so there is some room for a u-bend (downpipe) from the turbo into it, then another u-bend would come out and into the 4x9 previously mentioned.

Only potential problem I see is it's a 5x8 so it might be too thick. Then again, considering that I was going to use a 5x8 and 4x9 in this setup as a presilencer & muffler originally (they went into the GLC as a presilencer and muffler instead lol) perhaps there's enough room even with a turbo. I don't know.

But I do agree a single 4x9 won't be enough muffling. Even with a turbo, a rotary is leaps and bounds louder than a boinger and still requires a muffler. And what's worse is this is an S5 turbo with its wonderful nondivided housing. Steve says they're louder and raspier than S4s. All I know is PercentSevenC's FB has an S5 turbo with an RB 3" medium presilencer (they don't make these anymore - probably because they're largely ineffective) and then 3" tubing all the way into a magnaflow 5x8 18". His car is very loud. I can hear it in my house a little too well. I'm sure dropping component size to 2.5" would help but the downpipe has to remain 3" for quick spool - something I'm looking for in a baja for lots of low end, so I gotta use 3" as well, at least in the downpipe (or the first u-bend in my case).

So here's what I'm thinking: S5 turbo, horizontal downpipe 3" u-bend into the same side inlet/outlet 5x8 (thanks 13BT_RX3), then u-bend into the 4x9, then exit under the push-bar. I feel THIS will be enough muffling while not hurting flow too much. You gotta work within the space provided on these things.

An alternative would be to flow from the turbo into the 4x9, as it's pretty much straight through, then into the 5x8. This might keep the turbo happier.

 

The radiator does look like it takes up a fair amount of space, so getting the exhaust over to the other side may not be practical. I'm glad my suggestion added a tool to your arsenal for solving this problem. Do you have a picture from underneath that shows the space available?

I have another suggestion. Not as practical though. Make an active exhaust. Use a single large muffler to a tee with a boost actuated dump valve on one branch and a small diameter "quiet idle" muffler on the other.

 

Turns out the inlet/outlet on the same side isn't such a good idea on a rotary this close to the engine. Since the u-bend (if there is one) is a perforated tube, there is nothing to keep the exhaust velocity up like it does in a mandrel bent tube. So this will cause the muffler to heat up and fail quickly. I bet it's super restrictive as well. Maybe ok at the end of a system, as it was intended on a piston car, but not on a rotary this close to the engine.

So I'll do two 4x9s instead. Not too thick, center/offset for maximum installation possiblities, won't run too hot, will provide better muffling than a straight-through, and will fit better than a 5x8. Already ordered a length of straight tube and the u-bends. The walbro is here. Just waiting on one of the 4x9s and the turbo itself.

I'll probably get this running NA first to check how loud it's going to be, but somethng tells me to not even bother. It'll be too loud. I'm way too busy with other stuff anyway. But we'll see...

 

They showed up today. Now just waiting on the 4x9.

 

Hey its probably too late now but you probably should have just kept the whole system 2.5" right from the turbo outlet. I doubt 3" will make much difference considering all the other limitations of your packaging, all the bends etc etc.

Anyway Don't be too concerned about noise you are headed in the correct direction now, I previously had a 5x8x14 or so centre offest muffler under my rear space with a pair of long resonators that used the entire length of the car. That system was still quiet for a rotary after driving a non turbo.

That was a 3" mandrel bent dump pipe with a 2.5" press bent rear system. The difference between that system and the system I replaced it with was night and day, the full 3" much quieter (because of the monsterous 8x10x22 rear centre offset rear muffler and also clearly made much more power.

You are using mandrel bends? How long are your 4x9 mufflers?

 

The turbo is here! Well, it's still installed on the other guy's car, but I'll grab it today.

The 4x9 will be here later today. 14" shell (longer interfered with stuff). Yes, mandrel bends. Three of them, in 2.5" and one in 3", all 409 stainless 14 gauge. I chose 14 gauge because at the apex it's only 16 gauge.

So you say I should go full 2.5"? I understand what you're saying but why not have a shorty downpipe in 3"? They say it helps spool on these S5 turbos. I require fast spool to give low end torque. I don't need anything after 7k.

If it makes power past 7k, that's ok. But it's an old school R5 13B with 3mm apex seals and stock 12A Y ports. I only did a little smoothing of casting flash. Exhaust ports open at T2 spec but close at 2mm past US-spec old school 13Bs/12As which is a lot earlier than T2 spec. Hmm, I'd say they're similar to a 12AT exhaust timing, actually.

Hey I was recommended to go 2.25" after the 3" downpipe for this particular setup. I didn't like that idea too much so I chose 2.5" as the in-between size because it consists mainly of u-bends which are restrictive as an asthmatic hooker, and quiet as one too. Compared to 3" which is too loud for just two mufflers.

 

What are your power goals? For response and simplicity, I would consider just boosting the **** out of a stock turbo. You'll be capped at about 250hp, but the motor will make that at pretty much any rpm (big torque when boost hits, with a descending torque curve to redline). And when you destroy it, just replace it with another stocker.

Also: Plans for an intercooler?

 

No room for an intercooler.

But I do have access to a used motor to work out the bugs. If I pop it, no problem. I just don't want to break the nice engine.

Actually now that I think about it, there might be room for a small intercooler when the big radiator goes in. I gotta redo the cage anyway so I'll look into it.

 

Turns out you're supposed to keep it at one size on a system this small. So the downpipe will have to be 2.5".

 

Either way will work if you already have 3" keep it that way, if you haven't bought the parts buy for a 2.5" system.

Also regarding the intercooler.

I've tested both with and without on the exact turbo you will be using.

100% guarantee you in writing that it will be more responsive and faster with an intercooler on there.

Don't bother porting the motor, Is 12A Y a tall port? pictures of the porting configuration if you want.

Either way telling you now that a even a tallport 12A can 'suck down a whole s5 turbo' at 5500rpm and 13psi

Don't be so concerned with the boost drop off they still have excellent acceleration from 3500 to 8000rpm

 

I've got everything I need for a 2.5" system now.

Ok, if I can find room for an intercooler, I'll install one. Thanks.

It is a 13B with a 12A tall port Y intermediate plate. No porting at all (except some casting flash removal).

 

They look like 32 open 40 closing to me is that what you measured based off other known plates?