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Discussion Starter · #1 ·
I've been considering a Z as a candidate for a TT project. After awhile of lurking these forums along with a few others trying to sort out correct information and incorrect information I have a few questions. It seems the Z's engine isn't very FI "friendly". I see alot of mid 400 hp numbers which is decent but not great considering the size of the VQ compared to alot of other popular FI modded cars? And the fact it seems most making anything around 450 have lowered compression and other mods like cams along with a built block. My main question is has anyone hit the 500whp mark with a reliable engine running pump gas? I've seen numbers into the 500's but I'm assuming those were pulled with high octane race gas. Can the VQ not handle much more than 8 psi without having detonation issues on 93 octane? Running those power levels would be the ultimate goal for me but not at the cost of having to drive to the track every time I need to fill the gas tank.
 

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The VQ35 is a friendly engine for FI, but it needs to be kept under 400-450rwhp mark. With proper tuning the engine in stock form will be fine at these levels. In order to make more HP you will have to replace the internals, like the pistons and rods. This will only keep you safe up to 700rwhp. After that mark, you will need to close the deck by adding some sleeves to handle the power.

Now as for the 500 mark, it can be done on pump gas, I know of one or two that have done it. You can actually run as much psi as you want with pump gas as long as you set up your tuning properly. But you will have to change the engine internals.
 

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Discussion Starter · #3 ·
I've counted on changing the internals all along. There's no way I would try for that level of hp without it. My main concern was always being able to run pump gas. I guess I'm looking at a built engine, upgraded fuel system with a fuel return, TT kit, clutch/flywheel, most likely cams to hit that power mark?, does the VQ benefit much from head work with a FI setup? and tuning seems to be crucial. How well does the tranny and LSD hold up with power applications this high? Correct me if I'm wrong but I think the Z has a viscous LSD? I would think it wouldn't hold up too well. :headshake:

(Edit) What CR would be best for an application like this? I've seen anywhere from 9.1 to 8.5. Does it make much of a difference at that point? From what I've gathered lower compression = more boost but how much low rpm lag do you gain as you go down? I don't want it to be a dog from a complete stop in 1st until the turbos spool.

Sorry about all the questions. Trying to get a grasp on the whole FI subject. :burnout:
 

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I've counted on changing the internals all along. There's no way I would try for that level of hp without it. My main concern was always being able to run pump gas. I guess I'm looking at a built engine, upgraded fuel system with a fuel return, TT kit, clutch/flywheel, most likely cams to hit that power mark?, does the VQ benefit much from head work with a FI setup? and tuning seems to be crucial. How well does the tranny and LSD hold up with power applications this high? Correct me if I'm wrong but I think the Z has a viscous LSD? I would think it wouldn't hold up too well. :headshake:

(Edit) What CR would be best for an application like this? I've seen anywhere from 9.1 to 8.5. Does it make much of a difference at that point? From what I've gathered lower compression = more boost but how much low rpm lag do you gain as you go down? I don't want it to be a dog from a complete stop in 1st until the turbos spool.

Sorry about all the questions. Trying to get a grasp on the whole FI subject. :burnout:

I dropped my compression to 8.8:1 and did no headwork or cams.

If I did it over again, I would go 9.5:1 and maybe do a bit of head work.

I notice absoultely NO low end loss. In fact, my dynos have some of the best low end power I have seen. My problem was a lack of fuel up top. If you go TT, just make sure you get larger than 440 injectors and get a scalable EMS and 500 whp on pump gas is easily doable. I can still go for more HP, but honestly, IMO there is no reason to. My car is a solid 450 whp which is maybe 520-540 BHP. If you drove the Z with anything over 400 whp I am sure your attitude about 400 being just "decent" will change.
 

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Discussion Starter · #5 ·
If I did it over again, I would go 9.5:1 and maybe do a bit of head work.
What would be the advantage of the 9.5:1 CR and headwork instead of 8.8:1? I'm guessing with the headwork you'd get more air but at the same time you'd lose a few pounds of boost? I could be completely wrong which is why I'm asking. I come from a big displacement N/A background. FI is a completely new subject to me.
 

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What would be the advantage of the 9.5:1 CR and headwork instead of 8.8:1? I'm guessing with the headwork you'd get more air but at the same time you'd lose a few pounds of boost? I could be completely wrong which is why I'm asking. I come from a big displacement N/A background. FI is a completely new subject to me.
Well with a higher compression you can use less boost to get the HP and have good low end pre-boost response as well. With the forged internals the risk of higher compression is not like with stock internals.

Can you imagine an 11.5 CR forged block and boost :OMG: just kidding, when I get mine done it will be at least 9 CR
 

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Well with a higher compression you can use less boost to get the HP and have good low end pre-boost response as well. With the forged internals the risk of higher compression is not like with stock internals.

Can you imagine an 11.5 CR forged block and boost :OMG: just kidding, when I get mine done it will be at least 9 CR

The headwork will allow the engine to breath better, which is a definite plus for a TT setup. the higher compression will allow you to reach higher HP with a lower boost level. Realistically, it doesn't make a huge difference, you might need 1-2 lbs more boost to reach the same HP level, nothing major. In my case, I needed a lot more fuel at the upper RPM range in order to get to 500+ whp at my CR ratio.
 
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