Newb FI question

theDreamer · 11-15-2012, 05:53 PM

Quote:

Originally Posted by Boosted Performance

The car made 550whp even, and please note that the actual boost pressure at max HP is about 9psi (10psi at 6,000rpm and falling). The reason the boost is up in the early rpms was due to having a manual boost controller. Because it is a manual boost controller, there was no way to controll boost in the upper rpm's (like haveing an EBC and the option to increase the duty cycle). So it was turned up so that we can be as close to 10psi as possible at max power. As a result the boost was up to 12psi at 4500rpm.

The reason I say the 2.5" dual will make a lot of power is because of that graph. There is no sighn of it tapering off. It is just a nice linear line, with no dips, and no falling off at the top.

This is a Boosted Performance single, twin scroll turbo with a Precision 6266 billet T4 1.0 a/r. 3" down pipe to a Y-pipe going to the F.I dual 2.5" exhaust system with 14" resonators.

Did you stop at 7k RPMs? Because after there is a drop off.

Boosted Performance · 11-15-2012, 06:03 PM

Quote:

Originally Posted by theDreamer

Did you stop at 7k RPMs? Because after there is a drop off.

This would be a result of pulling timing, falling boost and flow limitation of the 1.0 a/r turbine housing...nothing to do with post turbo turbo exhaust.

Zeuz · 11-15-2012, 06:10 PM

Mr.Squeeze · 11-15-2012, 07:27 PM

Quote:

Originally Posted by Boosted Performance

This would be a result of pulling timing, falling boost and flow limitation of the 1.0 a/r turbine housing...nothing to do with post turbo turbo exhaust.

Sound's like the 6266 is comarable to the GTM stage 2 that's real nice.

Boosted Performance · 11-15-2012, 07:47 PM

Quote:

Originally Posted by Mr.Squeeze

Sound's like the 6266 is comarable to the GTM stage 2 that's real nice.

Yup, maybe even a bit more power because you can go up to a 1.32 a/r housing with the 6266. These egnines breathe so well, and rev very high....turbine housing size is key.

Mr.Squeeze · 11-15-2012, 07:58 PM

Quote:

Originally Posted by Boosted Performance

Yup, maybe even a bit more power because you can go up to a 1.32 a/r housing with the 6266. These egnines breathe so well, and rev very high....turbine housing size is key.

That's even more impressive, I learned the hard way housing size on my build not looking forward to swapping mine.

Boosted Performance · 11-15-2012, 08:16 PM

Quote:

Originally Posted by Mr.Squeeze

That's even more impressive, I learned the hard way housing size on my build not looking forward to swapping mine.

I think I remember posting in your build thread something along those lines, and somebody saying that upgrading to a dual 3" will make a world of difference. I can't remember now but I think you only made another 30whp? For comparison sakes, I just had a customer in at R/T with a 6266 T4 .81 a/r (open inlet) 350z make 610whp at 18psi. Vince said there was another 30whp left in the kit with that housing. So the .96 a/r would get over 650whp for sure. All pump gas numbers of course.

I did a lot of EBP (exhaust back pressure) monitoring when developing these kits for the 350z, so I also speak from experience...

. This is the main reason I only use the T4 turbine housing in all the VQ turbo kits.

I wish the 67mm turbos had a 70mm turbine wheel

really kick it up a notch.

SS_Firehawk · 11-16-2012, 02:58 AM

Just to clarify to everyone who thinks loss of back pressure means loss of low end tq. Your wrong. Because you have an enormous tube for an exhaust, it reduces the velocity of the exhaust leaving the motor. The domino effect is it reduces the scavenging effect or more simplistically, a vacuum effect of the exhaust assisting in pulling the gasses out of your cylinder. At low rpm, it's crucial in developing low end tq. The higher rpm you move up the power band, the less effect it will have because now the exhaust velocity is up to an acceptable point to continue scavenging. Exhaust size is critical to the amount of air your trying to move. A 3" dual exhaust will really only benefit you of your pushing 650-700hp at the crank or higher. 2.5" exhausts are perfectly sized for our motors until you start pushing some serious power.

Chuck33079 · 11-16-2012, 08:59 AM

Quote:

Originally Posted by SS_Firehawk

Just to clarify to everyone who thinks loss of back pressure means loss of low end tq. Your wrong. Because you have an enormous tube for an exhaust, it reduces the velocity of the exhaust leaving the motor. The domino effect is it reduces the scavenging effect or more simplistically, a vacuum effect of the exhaust assisting in pulling the gasses out of your cylinder. At low rpm, it's crucial in developing low end tq. The higher rpm you move up the power band, the less effect it will have because now the exhaust velocity is up to an acceptable point to continue scavenging. Exhaust size is critical to the amount of air your trying to move. A 3" dual exhaust will really only benefit you of your pushing 650-700hp at the crank or higher. 2.5" exhausts are perfectly sized for our motors until you start pushing some serious power.

This is entirely correct. To be fair though, this is usually what people are talking about when they claim "a naturally aspirated engine needs backpressure". Kinda like the confusion between tubo lag and boost threshold. Most people have the right idea and the wrong terminology.

11-15-2012, 06:10 PM	#33 (permalink)
Zeuz Enthusiast Member Join Date: Oct 2011 Location: Houston Texas Posts: 292 Drives: 2011 370z Rep Power: 13	__________________ Advant M310 // Tommy Shifter // Swift Springs // Fairlady Emblem // Seibon // Stillen //

11-16-2012, 02:58 AM	#38 (permalink)
SS_Firehawk Premium Member Join Date: Oct 2011 Location: Tampa Posts: 4,142 Drives: 13' Magma Red Nismo Rep Power: 7334	Just to clarify to everyone who thinks loss of back pressure means loss of low end tq. Your wrong. Because you have an enormous tube for an exhaust, it reduces the velocity of the exhaust leaving the motor. The domino effect is it reduces the scavenging effect or more simplistically, a vacuum effect of the exhaust assisting in pulling the gasses out of your cylinder. At low rpm, it's crucial in developing low end tq. The higher rpm you move up the power band, the less effect it will have because now the exhaust velocity is up to an acceptable point to continue scavenging. Exhaust size is critical to the amount of air your trying to move. A 3" dual exhaust will really only benefit you of your pushing 650-700hp at the crank or higher. 2.5" exhausts are perfectly sized for our motors until you start pushing some serious power. Chuck33079, DEpointfive0 and Z-Girl 12 like this. __________________ Old Car:GTM TSC'd 550whp / 410lbft tq @ 11.88PSI New Car: Under Construction

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