Secondary delete on mildly modified Z..

[Vette73]

As you can tell from my previous posts I'm looking to get some additional work to my 91.......Does removing the secondary's provide an additional " seat of the pants feel"....

[efnfast]

No.

[G8nightman]

Seat of the pants feel is going to cost another 20 to 30 grand.

[XfireZ51]

SOTP is highly inaccurate.

[Paul Workman]

According to this Lingenfelter graph the LT5* will produce as much as ≈ 40-50 foot# MORE torque with the SPTs turned OFF when the RPM is in the 2500 to 3400 RPM range.

Above approx 3400 RPM the low-end advantage rapidly tapers off to ZERO compared to the FULL ENGINE POWER mode).



This low-end characteristic torque advantage of the (stock) LT5 has little practical use except below ≈ 4000 RPM when running WOT while the SPT switch is in the NORMAL setting, e.g., in city traffic, perhaps. But, after ≈ 3400 RPM the advantage of leaving the SPTs in NORMAL mode fades to nothing compared to the FULL ENGINE POWER mode.

However, after the LT5 is fully ported and headers added, this "before and after" graph shows how the porting results in a gain in the low-end torque which NEARLY mitigates the advantage of the stock LT5 in the NORMAL power mode. (And, on a fully ported motor, operating in NORMAL mode is likely moot, as the secondary ports are often opened beyond the stock 36mm throttle plate diameter - which leaves the SPTs literally "hanging in the breeze".)

*Aside from retaining the STPs, modifications (if any) to the Lingenfelter motor are unspecified. Therefore any comparisons between the two graphs are only relative at best, i.e., apples and oranges to a greater extent.

[Vette73]

Originally Posted by Paul Workman

According to this Lingenfelter graph the LT5* will produce as much as ≈ 40-50 foot# MORE torque with the SPTs turned OFF when the RPM is in the 2500 to 3400 RPM range.

Above approx 3400 RPM the low-end advantage rapidly tapers off to ZERO compared to the FULL ENGINE POWER mode).



This low-end characteristic torque advantage of the (stock) LT5 has little practical use except below ≈ 4000 RPM when running WOT while the SPT switch is in the NORMAL setting, e.g., in city traffic, perhaps. But, after ≈ 3400 RPM the advantage of leaving the SPTs in NORMAL mode fades to nothing compared to the FULL ENGINE POWER mode.

However, after the LT5 is fully ported and headers added, this "before and after" graph shows how the porting results in a gain in the low-end torque which NEARLY mitigates the advantage of the stock LT5 in the NORMAL power mode. (And, on a fully ported motor, operating in NORMAL mode is likely moot, as the secondary ports are often opened beyond the stock 36mm throttle plate diameter - which leaves the SPTs literally "hanging in the breeze".)

*Aside from retaining the STPs, modifications (if any) to the Lingenfelter motor are unspecified. Therefore any comparisons between the two graphs are only relative at best, i.e., apples and oranges to a greater extent.

Hey thanks for the info Paul.....So basically that graph is showing a 500 package Z as opposed to a stock Z.......What it's showing is there about even up to 3,400 RPM....Excuse the ignorance but SPT is secondary port throttle correct?

According to the graph were both motors tested with the full power key on? Of course they were correct?

[Vette73]

Originally Posted by G8nightman

Seat of the pants feel is going to cost another 20 to 30 grand.

Lol...Hey thanks for the advice....Hey how's everything going? I'll see which direction I'm going to go with the Z......I was up early last Sunday so I took a ride to Captree by Jones beach.......Don't know if you have ever been there on Sunday but it attracts hundreds of nice cars.......Needless to say you can open it up on Ocean pkwy if need be....

I'll drop you a PM if I decide to go again,if we have some decent weather in December and I have the car back...

Hope alls well...

John...

[Demps]

I researched but didn't see if you have installed lower rear gears yet. That's probably the best seat of the pants per dollar mod. If you have, well...get ready.

If the LT5 is your thing (because there's better places to spend money for power if not) go stroker early.

Ted

Stock
Bolt ons
Ported
Ported & gears
Stroked & gears

[BigIke]

I had a good SOTP feel in my car... Even before the MH-tune. I'd recommend it; heck, it only takes 30-min to pull the upper... My vacuum secondaries were working fine as well.

[Blue Flame Restorations]

Removing *ripping out" the secondaries just helps to eliminate vacuum leaks. If you want seat of the pants driving, get a set of 4:10 gears.

Porting and cams will make a "Yuge" difference.