GTM Stage 2 Supercharger Preliminary Testing Results

XwChriswX

See here:



Looks pretty identical to me...

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Bonnie - Stage 2, Audio build coming this fall!
R.I.P. Abby 3/29/10 - 3/30/14

frostyrock7c

Agreed... strange indeed.

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2009 Nismo 370Z #0136
The past... 2008 STi stock thanks to questionable ringlands, 2005 STi modded and very fast, 2004.5 350Z modded and fast-ish

fstrnldr

Still confused why someone would go through the time to make a long tube head but not make it equal length.

Anyway since when is it GTMs responsibility to test their products for compatibility against other non OE manufacturers offerings? Maybe they didn't feel like spending the money and time to see if a part that offers them no income from sales fits w/ their kit. Maybe there is something that can't be seen in those pictures. Or maybe it is a heat issue. The fact that the OE piece is two layer steel + a heat shield (keeping more radiated heat inside the pipe) vs the aftermarket piece which is single wall tubing with no coatings or heat shields could play a big factor.

wstar

The FI LTH come in a ceramic coating for heat shielding. I suspect the walls are thicker too, though it's been a long while since I've seen my stock manifolds. Neither GTM nor FI are responsible for cross-testing with each others' products, but I think it is reasonable to ask that FI know and disclose any effect the LTH would have on an SC setup in general, and for GTM to know and disclose any effect a cat-less or LTH exhaust flow is going to have on their SC kit and why.

Both seem to have done so, and they come to conflicting conclusions. I don't have enough personal data or expertise to weigh in any further than they have already.

Some independent parties (e.g. theDreamer) have combined them and think there's no real issue given a proper tune though. Given FI's recounting of Shumby's experience, I'm not sure I put a lot of weight in that story one way or the other, just too little hard data and not enough experimenting done.

For reference, the very bottom of the top post here has FI's conclusions: Fast Intentions Long Tube Headers are here!

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7AT Track Car!
Journal thread / Car setup details

ND370z

GTMs responsibility to test their products for compatibility against other non OE manufacturers offerings?

I think thats true. GTM should be concerned about there products.
I can care less about the LTH. Especially at that price point.


But i want to see the press release and any updated info. I heard sam is working on the Automatic SC install still?

branz1029

Very well written write up..... Thanks

1slow370

Its quite simple really in a naturally aspirated engine with stock exhaust, the valve overlap on the engine allows the exhaust volume moving out of the head to scavenge the cylinder better allowing a greater intake volume to be pulled into the cylinder, it is timed up so that the valve closes before the intake charge begins to leave the exhaust valve. When you put headers on an NA car you improve the scavenging of the exhaust improving the intake charge to the point that just a little intake volume goes into the exhaust before the valve closes but the cylinder is filled with more intake charge regardless so it makes more power. On a supercharged car the intake charge is pressurized so that once the exhaust has vented enough that the cylinder pressure is equal to the intake pressure intake charge begins to flood out the exhaust valve long before it is closed, with a restrictor like a factory cat, or running a smaller exhaust diameter(2-2.5") with test pipes you allow manifold pressure to rise right at the critical point where the intake charge would over pressure the cylinder and flood out the open exhaust valve so the manifold back pressure holds the charge in.

This has been true for long before the 370z even came out, every supercharger kit manufacturer will warn about headers causing a loss in boost pressure, the fact is with a supercharger and the locked in cam timing the Z will make more power per cfm pumped into the engine with a restrictive exhaust. headers plus cam timing the way it is the engine wastes a large percentage of intake charge, so the header manufacturer tells you to get a bigger blower so that even though 10% of the intake charge is flying out the exhaust you will get your power back by shoving more in. The supercharger manufacturer tells you to put a more restrictive exhaust on the car so you waste less and get more pressure and power for the amount you spin the charger. In the end the both do the same thing you just have to pick whether you want headers and a more wasteful setup or a smaller setup that's more efficient.

Now if you can change the valve timing, grab your self some headers and turn the overlap down and enjoy the best of both worlds. Like I said none of this is new it's neither companies fault it's just the way it is, thats why back in the 60's a thing called a blower cam was invented.

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