I've read a few times on AUS300zx that ported stock manis with upgraded turbos aid spool up time, over having a large aftermarket exhaust mani, such as the AMS one. On numerous websites selling the larger manis, the claims are that bigger manifolds aid turbo spool? Are there dyno graphs/measurements anywhere proving this or shall I email the 'Mythbusters' team to get them to prove/disprove this?
Turbos spool from pressure. Bigger manis means higher volume of space for the exhaust gas means less pressure. Less spool. Though bigger turbos means it doesn't take long to make enough pressure to create a bottleneck. Make a manifold the size of a bathtub and see how the spool is
also 'flow'... but obviously that comes more into play for max HP at high RPM. I like the bathtub idea...
Heat is a factor of pressure. But air pressure difference is the reason it spins. Hold a 1000degree molten metal poker against the exhaust wheel and see how fast it spins? Too much pressure in the exhaust manifold means too much backpressure for the engine and its a system bottleneck.
Many many many factors determine spool up. The major question to ask is where in the rev range you want maximum HP and torque. The VQ engine in standard form is designed around delivering torque pretty much from idle on up. Of course you can bolt on those mega wide exhausts and huge turbos and get %^&* all of either until you hit the redline then all hell breaks loose
Id be very surprised if you could conclusively prove or disprove any claim made against a manifold as agricultural as a Zed turbo manifold in the real world with regards to internal diameter alone. Im sure that some regular porting, smoothing as many edges and reducing turbulence would be a good thing but they are a dreadful "log" style of manifold made with a view to commercial expediency rather than any real performance potential and it rubbish to begin with. That manifold is no better designed than the manifold on my old Fergy 28... no, wait.. The fergy is probably better due to the individual runners all merging nicely rather than at almost right angles!!!!! Almost right angled turns for the gas to travel, horrid little bumps, lumps and corners, gas pressure reversion up the unused ports possibly interfering with any possible extractor effect and finally having to shove all that disturbed airflow and heat down the laughably tiny inducer of the turbine wheel! Go on, take a look in there on an old turbo, youll be lucky to fit your finger thru the hole and somebody is concerned about a couple of extra MM's up in the log and figures it the holy grail of turbo boost and power!!! Baaahahahaha! I cant see that manifold working a lot better than a simple box, or plenum, exactly the same as an inlet plenum, bolted to the side of the engine with the turbo hanging off one end!!!! Bloody big heat radiator tho!!! Might look kinda strange. Actually, with good design, id expect a box to actually work better!!!! Well?? You spend a shitload on custom plenums on the inlet to increase power. Why not on the out side eh? As far as the internal diameter and pressure drop and so-on, the theory is sound but in practise its just not an issue. Really, look at the internal volume of that pissy little log... what a couple of hundred CC's??? Its a similar argument for larger and larger cooler pipes. The laughably rediculous notion that the Pressure "wave" will take a measureable amount of time to travel from one end of the pipe to the other, pressurising the system as it travels along and your cylinders having to "wait' while the pooor little air pump slowly fills the pipes with pressure is as humourous as it is preposterous!!!!! Its the fundamental design and finished product which is the real problem. You want to have a good setup. A carefully designed set of equal length and tuned extractors with the turbos hanging off each end should yield demonstrable power increases!!!!!!!! Fat chance if that in a Zed!!!!!!!!! LOL L8r E
Pentroof used to make a good manifold... Rare as hens teeth I just wish there was room to fit NA extractors on a zed and have somewhere to fit the turbos... BAH!
I'm sure you could find a set of pentroof manis if you really wanted to. I wouldn't fit a staino tubular manifold though... yes they look good and have lots of nice features but they are bound to crack sooner or later. Probably not a big deal in a race car that gets pulled down every season but not a good choice for something you only want to put together once. Cast log style manifolds by comparisson are super strong.
Link to a single Pentroof manifold for the Z that has cracked please. They're still listed on OOPARTS International but they're listed backorder. For what they're asking for them though they're not even worthwhile considering IMHO.
Hmm just did a search and you are right I can't find any examples of pentroof cracking. Plenty of Trust/Greddy/SpecialtyZ/otherknockoff stainless manifolds cracking. I'm sure if you ran pentroof manifolds on a car long enough you would run into problems -stainless tubular design just isn't a good choice for Z32 manifolds considering the weight and heat cycles that the manifolds are subjected to.
Oooohhh... nah, the NA pipes are pretty dodgey inside. They look trick hidden inside all that shrouding and heat insulation but when exposed, they dont merge well and are probably only a vague step up from the cast TT Logs. Unless your talking something aftermarket and merged. L8r E
The merges are absolutely horrible and there is a lot of overlap where they are joined together. I had some piccies of one cut up, will dig them up later.
The Pentroof manifolds were made from inconel, the same material as shipping containers and TT exhaust valves, thats why they didn't crack
Now who wants to copy some original Pentroof manifolds with inconel and make some money? hmm? hmm? P.S. who has originals to copy that aren't fitted to a car?
Source? Everywhere I've read has them made from 304 SS, confirmed by Kuah @Splparts. Sure you are not confusing them for the Inconel manifolds that SpecialtyZ produced? According to here Z1 also made a Inconel manifold that were tubular but eveyrthing I've seen says that legit Pentroof manifolds were 304 SS.
Bwaaaaaaaaaaaahahahahahahahahha SHIPPING CONTAINERS???????? Be the most expensive, lightweight and brittle metal boxes in the world. LMAO! Nah m8, containers are made out of CORTEN steel!! L8r E
So final verdict is it a yay or nay for larger AMS/MS manifolds??? Serveral dyno charts from Greg at Specialty Z show that there are significant gains to be had even with stock engines and turbos. I expect that there would be gains on a rebulit engine that has had head work (porting and oversize valves). If the exhaust ports are opened up to the same size as the AMS manifolds surely there will be increase in response and torque. Reason I ask is that I have AMS manifolds though should I go ahead with using them on standard turbos?
I'm now very skeptical about results from any company with something to gain from results... If ur going to pull ur engine to fit the manifolds... Don't... Just save up and buy bigger turbos and install them while ur there. I'll wager a bet with anyone who reckons the bigger mani's will yield enough hp return to warrant the upgrade. Well on stock turbos anyways...
