discopotato03

I will ring Kevin in a few days because I'm curious to know if two of his larger mufflers can silence a 3 1/2 system on a GTS25T with a GT3076R . Dump to cat is already 3.5 just need the rest . By quiet I mean REAL quiet and no drone . Steel is fine too . Cheers Adrian .

From what I read at FPs site the GT3794HTA is the largest of the GT35R based units thought it's supposed to have a GT37 sized turbine with the 94HTA wheel . The Super 94 they say is based on 10mm rather than 8mm bearings so I gather they've moved up a Garrett GT cartridge size to the one used in the "T4R" series like P/60-1 and T04Z . These cartridges use bolt on back plates like the old T3 T4 etc and they use whats known as GT40 series compressor housings . Actually the 60-1 and T04Z versions used a cast iron back plate designed to mount the familiar T04S comp housing . GT40 comp housings don't have to be huge and you see them on bush bearing GT37 and GT40 turbos , from memory the GT4082 uses a 0.58 comp hsg . Also look at pics of GT4088Rs to see more conventionally configured GT40 comp housings . I think FP has been doing GT37 and GT40 based HTA turbos for a while now . A .

The T04R wheel that gets used in those "GT35/T04Z conversions is not exactly a modern wheel and I think a decent billet compressor would do better . You could have a V band adapter machined up and welded to your housing to create a 3" or larger outlet on the same cone angle as the housing . A .

I'm interested to hear about the maximum size of mufflers that will fit under R32s and R33s . I had my R33 (GTST) measured recently and it has a Nismo Jasma I assume 3" cat back ATM . I wanted mufflers at least as large but I'm not sure anyone does a 5 x 10 x 16 for the mid one . It's interesting that Kevin did an 18 x 7 round rear one because David Buschur in the US used a Magnaflow 14 x 7 round on his quiet "diff back" for Evo Lancers . I was told a 6 x 11 x 20 oval would go in the back of my R33 though I'd rather try a 7 x 18-20 round if it can fit . If Kevin can do the same size as the middle Nizmo one - or better - I'd like two mufflers please . There is limited space between the upper side of the mid muffler and the tailshaft so it's a bit of a juggle . One other thing is where the cats located . If it could be moved further forward a third resonator could possibly go where the cat was and quieten things down even further . I mention this because the Americans sometimes fit another muffler where the cat was and run catless which is risky on the street . They reckon a 6 x 14 Magnaflow round in the cats location makes a noticeable difference with the 7 x 14 round at the back . Just yesterday I read a long thread on Evom.net about a bloke that wanted a factory standard sounding Evo with a 3' aftermarket exhaust . The closest he got was with a Dynomax VT , valve technology ? , muffler with a lightly spring loaded valve in the back of it . It worked well but the valve rattled badly at idle partically on engines with big cams in them . Anyway quiet free flowing mufflers for Skylines in 3-3 1/2" would be great , cheers Adrian .

Grape vine reckons the four bolt ext type GT30/35 housings are to be phased out for V band ones .

The measure up shows that at the back a 6 x 11 x 20 oval will fit , the mid one is 5 x 10 x 16 but they don't reckon anyone does a 5 x 10 . KiwiRS4T you mentioned that your Venom 5" body cat is welded into your front pipe , is your cat in the std location or further forward ? The reason I ask is because in the US they sometimes flick the cat a use a "resonated cat pipe" to help shut evos up . Also Buschur offers a "diff back" pipe for Evos that has a 7 x 14" round Magnaflow instead of an oval . The claim is that round work better than ovals because of the depth of the packing above and below the straight perforated tube . Thoughts ? Cheers A .

The Americans could do worse than develop sub Green BB hi flows but the issue is probably chasing Rex performance with a 2L vs 2.5L . It's a big call trying to match a conventionally turbocharged 2.5 and technology is hard pushed to cover the torque hole at low revs with 2 litres . The aftermarket wants the numbers and puts up with lag in the hole because of it IMO . Probably why every second LHD Evo has a stroked motor too - 300cc lag bridge .. I'm not sure if FP or anyone else uses a turbine smaller than FPs 65mm other than the TD06SL2 . At one stage GT Pumps did a Green HTA/SL2 but that was a locally brewed bush bearing turbo - I think they use their own billet wheel now . I reckon concentrating on that punch is everything in an Evo because that's what they were designed to do . Maybe another way to look at it is take 4/5ths of what the RB25 did and aim for numbers like that . 80% of 330 is 265 and whilst that may not sound like a lot it could add up to more usable low to mid range punch than a 280+ WKW 4G63T . A .

GT yes the go will be to use the cat "cones" as a reducer ie 3.5 in and 3 out , bolt on solution . A .

So much reading on exhausts . I searched to see if the Japs did anything and all I came up with was Kakimotos that looked good but had a few surprises inside . A cannon is out , hate the look , but why do they try to rip everyone . At one stage I bought a second hand Evo 6 HKS Silent something and it's plain to see they think everyone wants the BIG look . They start out with something like 63-70mm from the cat to the mid muffler/hot dog then step up again from there to the rear muffler/cannon in 80mm . The rear muffler has conical entry and exits in its perforated tube so nothing like 80 anyway . The outlet is something you'd nearly get your head in , the big one ... If you have to change exhaust diameter it makes sense to start out large and end up smaller IMO , some hope of the gas cooling and shrinking and maintaining velocity through the mufflers - in theory . I see zero logic in having tube increases after mufflers because losing gas speed there is a backwards step . I think the path is 3" tube with 3" mufflers , plenty big enough for the power and no idiotic gas speed increases / decreases for lunatic value ... A .

Magnaflow are doing 5x11x22" ovals in 76mm , would these fit an R33 mid and rear or too long ? Mine has a lock bar rather than rack at the back if that makes any difference space wise . Cheers A .

Ok so what combinations of oval mufflers are we using in 3" systems , bigger can area better IMO so do any off the shelf use all the available space ? The quieter the better . Also I'm keen to lose the 5 inch or whatever Jap rear outlet for a 3 inch one . A.

If you can special order cartridge number 446179-21 that's what "2530s" use from memory . Other wise if you can find used 2530s they can be rebuilt because all that's unique is the housings and compressor wheels . A .

Well we should put the Viagra eye drops in and take a good long look at this ... Seriously though Ford changed the game a bit with their XR6Ts because they turbocharged a biggish straight 6 with a Garrett GT BB turbo . Compared to a base line GTS25T the XR6T is approximately 23% heavier with 60% more capacity , using 1385 Kg vs 1700 Kg . From memory a Typhoon makes over 300 std where the GTS25T made a little under 200 std so ~ 50% . The tell all would be to fit a GT3076R to a GTS25T with the XR6Ts exhaust cut up and rejigged under the Skyline and screw the boost up . Anyhow people are making the numbers (300+ WWasps) with 3" exhausts so it obviously works , I assume that's what Micko used for his 330 odd Kw car ? The reason I mentioned 3 1/2" is because that's what my dump and front pipe is and ATM it has a 3" bore cat bolted to it (same flange profile) , not a great situation . It makes sense to use a better cat than a guesses 3" bore 3-400 cpi ceramic one and if a 5" body Venom 200 cell one with a 3 1/2" inlet goes bolt it's all good . The question then is do I use the tapered cat outlet to reduce to 3" or keep the larger tube size back to the first or possibly second muffler . The big question is drone and noise and I can live without both as much as possible . I should state my aims which are to give the engine the best volumetric efficiency I can because the theory is that it works as better air pump on and off boost . Now people like Corky said that the best turbo exhaust is no exhaust because the greater pressure drop across the turbine makes it easier to spin up . My previous experience with the ancient Subaru EA82T engine was that a 3" front into a 2 1/2" exhaust behind the cat worked well for a guesses 150 max Hp and it wasn't noisy . To put you in the picture we made up an almost equal length header for it and plumbed a dinky GT2554R into it which was if anything a little big . A exhaust of that size you'd think was way too big for a 1800cc four with ONE exhaust port per head/pair of cylinders . Horrible heads with small ports and the siamesed exhaust ones . One engine pipe off each trying to feed the smallest available GT BB turbo , 0.64 AR T hsg because I didn't know a weird 0.56 one existed till too late . Stone age engine aside an exhaust that by rights should never have worked did - and wasn't noisy . Any way my RB build has included OS exhaust valves and 256 Tomeis mainly to get the exhaust and heat out of this thing quickly and easily , this is effectively what later engines do because they run so lean and hot that if they don't reject the heat efficiently they cook - literally . For me this 0.82 GT30 is boarder line a tad big so I need the most part throttle power (torque) I can get in pre boost mode to narrow the gap from NA to forced states . If the engine works better before boost and the turbo can be coaxed to spin up a tad earlier then it's a win I reckon . Of course least exhaust restriction is where power is to be made with the boot in and turbo up to speed . I think these days that the "tuned" nature of an exhaust behind a turbo is less important than an NA engine is behind its exhaust manifold because of how the manifold and housing is designed to feed a rotary turbine . It's hard to imagine exhaust gas reversion back up the exhaust through the turbine housing and manifold unless they are really huge and or the engine has really big cams . If anything having a small turbine/housing/exhaust off it - is probably worse in every way except heating up the cat for emissions . Anyway there obviously comes a time when the exhaust gets that big that there is minimal "backpressure" and going bigger doesn't achieve very much . Realistically tapering down behind the cat is probably way to go because there is probably enough volume in the larger front pipe and hopefully free flowing exhaust to get enough pressure drop across the turbine to wake the turbo up and make adequate street power . The 5" body 200 cel Venom cat is a good compromise IMO (flow/smell) and if it acts as a 3 1/2 to 3" reducer at the same time it's an easy bolt in . A .

Has anyone had success using that freeze spray bearing places sell to shrink the studs enough to get them out ? A .

Be good to have a local account of an FP bolt on , I gather it's a BB green ? From memory they have a larger turbine than a 3076R and the 73HTA compressor . I always wondered if they'd ever do a BB White or 71HTA but the Americans like to chase numbers . Hope it works well cheers A .

Gary I think the cooling theory holds water but possibly more of an NA than forced principle . The exhaust people I speak to say that from dyno experience 3.5 is where it's at power wise approaching 300 RWKW . This is not to say that 300+ can't be done with 3" though no two built exhausts will be exactly the same . I have to compromise because my 33 is a daily and loud exhausts isn't an option . I have considered and did ask about staying 3.5 through the cat and first muffler and stepping down for the rear one , half way and easy to change if that was quiet . Realistically 3" after the cat is probably acceptable 90% of the time for a car that isn't raced on or off public roads . Interested in other opinions , cheers A .

Seems like everyone likes the 100 cel 5" body Venom . I need something that's at least 3.5: inlet because that's what my front pipe is . The exhaust mob I use showed me a generic Xforce with long gentle taper cones and was thinking of cutting one end back at 3.5" . Gotta make sure they can do that socket joint in 3.5 as well . Just spoke to George and he may be able to do me a 5" body 200 cell cat that's plenty good for ~ 300 wasps and not smell pulpy . Thanks , A .

Looking round for good high flow cats and the ones that look ok are the 3.5" 200 CPSI Xforce and Venom ones . I'm thinking slightly larger body and 200 rather than 100 cell core so it may at least smell like its doing something usefull . I'm not interested in bore size discussion because its enough to say 3.5 cat on 3.5 front pipe and neck down behind the hot bit . OD size is obviously important because it has the clear the floor pan and not sit too low . 4 4.5 and 5" ODs get mentioned so are the big diameter ones hard to fit > A ,

I caught up with the exhaust people late this afternoon and there opinions are . Existing cat is RS and needs to be replaced by something better , they like 100 cel metal core ones . They asked the power goal and say 300 tread wasps is around the 3-3.5" cusp . 3 quieter but 300+ grey area . They use 3.5 on XR6s which is logical on a 4L IMO . Dale my exhaust already has two oval mufflers and clearance isn't an issue . I roll on 245 45 17s and no it's not low for a Skyline . Anyway the plan is to get it on the hoist and have a good look at what's there . The cats going and I finally found someone who agrees that those spring loaded "cup joints" are a good idea and keeps them in stock . The rally people who used to do my exhaust work said big exhausts act as great engine steady bars meaning they transmit a lot of noise and vibration into the system and often they ring like a bloody bell . Naturally this is transmitted into the cabin space pissing the ocupants off no end . If this cup joint can go behind the gearbox hanger it will unload the exhaust and very likely give the manifold studs an easier time . The plan is to have 3.5" to the cat and probably taper down to 3 behind it for for the mid and rear mufflers . The rear to have as much can area as possible . Anyway joint and cat first and suss out the rest . A .

Yep they are 3" through on the later BF Turbos and people say their std exhaust is god for around 320 Kw . The twin pipes and mufflers looks like an interesting idea too . Not conformed yet by my exhaust may be a HKS Drager with oval mufflers mid and rear , will confirm later . Anyone else have this kind of thing with the two internal pipes in the rear oval ? A .

Thanks for that Scott , I sort of wondered if Neo differences had much say but probably not a lot in this case . I was hoping to get some exhaust feedback like best flow with least noise . From searching it seems quiet exhausts have custom (largest can area for the space) straight through mufflers mid and rear and aftermarket race type cats . I wonder if I continued back in 3.5" for the cat and mid muffler and kept the rear 3" it could work alright . I don't have a lot of faith in my rear muffler and not sure what the offset centre mid Nismo muffler is like either . And Cats , I suppose any aftermarket one isn't cop proof so is there any OE one out there from a big capacity car/truck that looks OE ? A .

So I gather it floats clear of the turbo itself being mounted to the tower . A .

Thanks for that , must have been another pic of your setup I mentioned earlier and that's about as inoffensive as an external set up gets to look on a 25 with a std manifold I reckon . A .

Chuckles , no not touching that turbo/housing ATM because there are other things to look into . The actuator is a large can 1 bar Garrett one and the preload was set by GCG . Boost control is I think a Mac valve run by the "V66" plug in . I wouldn't have thought with that housing the valve would be blown open but more on that in a minute . I did a bit of fine tuning yesterday because I went back to E35 and changing the fuel trim only gets you in the ballpark . It's a juggle of getting acceptable idle pulse widths and mixture control at idle with these Denso side feeds - more eth means better control . I digress ..... I fill to the neck to do my consumption calcs and ATM it's doing better than any previous memory so at round town loads/revs its exhaling more easily . Don't be shocked people because I'm probably the only Skypilot without an aftermarket boost gauge , std one tells me the important stuff and is backed up by the lap top when online . So , it tells me that up to atmo manifold pressure not that much has changed with the turbo and it can be coaxed into positive briefly at open throttle high gear low revs . Under medium acceleration loads manifold pressure goes positive particularly on gentle rising grades . Just once I heard the faintest little whistle with the boot at ~ 3500 revs . Now , I'm beginning to think this turbo is trying but something is getting in the way of it spooling freely in the 3000+ range and my exhaust could be part of that . It's a Japanese aftermarket one and very probably a HKS one because my car was imported with RS HKS dampers and rebranded Rays LMGT4 wheels . Previous experience with Jap aftermarket Evo exhausts is that they use smaller diameter tube where it can't be seen and fat stuff out the back . Mine isn't like that but the rear muffler has two tubes through its guts that half underlap the cans rear hole if you get my meaning . There's a pic of it in the other GT30 fitting hardware thread . If something in the pipe is restricting turbo response won't be famous and maybe liveable with a GT28 hot side questionable with a 0.82 GT30 one . And the cold side . People here may be able to tell me where you hit the wall with the std air box and snorkel . It still has the Z32 leading to Scottys 80mm induction pipe and a silicon step up to the comp housings 100mm boss . The box has a washable panel filter I got off Fabre Midel and SK said they were better than K&N . It was cleaned a while back and will be today or tomorrow . In an old thread here at SAu someone else found the std box to run out of flow somewhere in the 320+ RWKW range which I wouldn't have ATM . Anyway I reckon exhaust could be the place to start and I even considered 3.5 inch but not certain it could be made quiet enough . I noticed UAS do a 3" 33 GTR exhaust that's based on standard muffler positioning and style , twin outlets instead of the 5-6" OD dick extension Japs brands like to use . On the inlet side a 33 GTR box may fit with a bit of stuffing around into the suction pipe . I don't want to think too far ahead with other turbos yet , yes the 0.63 AR GTX3067R should boost sooner than any 3076R and is probably be a better upgrade from a GTRS if you wanted shove from say 2800-3000 revs - guesses 2835 Pros Style . If I hadn't had the 52T already I would have thought harder about the 67R . TBH a number got in the way and 300 RWKW was my aiming point where realistically an efficient responsive 280+ would surely adequate - for me anyway . Anyway opinions about exhausts and inlet systems I'd like to hear inc cats . Thanks all , cheers A .

I know what a TD05HR-16G6 drives like on a 4G63T but the dynamic of that engine is totally different to an RB25 . It's well know that a 20g compressor turns those turbos into a laggy dog , very easy conversion for a lack lustre result . I have a second series TiAL/Magnesium Evo 9 turbo that may one day go on the Evo if I keep it long enough . Same size wheels in lighter materials with updated housings that will make enough power and be more responsive than a 6 GSR turbo . Always controversy with GT30 based BB turbos , they have their place but get the cold side wrong the well worn path is 4-7000+ rev power potential . The 52T 3037 may not be a game changer but anything that gets that turbine off it's arse without a smaller turbine housing is worth having IMO . I can feel it plain as day that this turbo wants to spin up but the issue is the transition from spinning to meaningful boosting , it's the gap between positive manifold pressure and the power surge that appears to be wide atm .