After driving this thing for a while, here's an unbiased review of the my GTM-built 420Ztt.

Picked her up in Rancho Cucamonga, CA, and drove in the heavy LA traffic daily for a week while visiting my gf who just moved there. Outside temps reached around 95 degrees F, and the car was running hot due to the bigger engine. When driving, water temps hit around 210 degrees, and oil hits around 225 degrees. Keep in mind this is heavy stop-and-go traffic. Once the car gets to highway cruising speeds, water goes down to about 190 degrees and oil temps go down to about the same. So the car is very stable. However, when I pulled into the gas station and left my hood closed, after filling up and starting her up again, water temp would hit about 220 degrees...and of course cools down right after. All in the safe range still.

Drove about 500 miles total in the LA area in the week I was there. Power is everywhere from 3000 rpms onwards. This is with the APS Extreme TT. Pretty much once it hits 3000rpms, the car would go sideways if I push the pedal to the metal. It's fun, but of course I'd have to squeeze the throttle a bit. The torque is so strong that VDC couldn't even kick in in time sometimes.

There is still a slight lag to the turbos, slightly more noticeable than the standard APS TT, even with the 4.24L stroker. But the car runs flawlessly, despite the occasional heat soak in bumper-to-bumper traffic.

I'm running 285 rear Toyo T1R's right now, so obviously traction is out the window. Currently running low boost at around 12psi (wastegate pressure) and making 600+rwhp / 600+rwtq. This is already a handful on the street. But the Fcon Vpro is very easy to live with, which makes the car drive pretty much like how a stock car would, but with boost of course. The only downside is when it gets hot, the hard starts make the initial idle very rough. But that'll be sorted out soon by Sam.

Even when pushing the car occasionally on the street, I'm shifting around 5500 - 6000rpms, because 1) it shoots up way too fast, and 2) I don't have much traction.

AFR's remain stable, and it's running slightly rich purposely to give me a cushion of reliability. Of course, no knock whatsoever.

The engine sounds amazing. The engine itself is a little raspy, making it sound very tough, and to the people that know what they're talking about, it does sound like a stroker in every way. But when you pop the hood, it just looks like a standard APS TT'ed Z.

Also running the Greddy EvoTT exhaust, and everything's still flowing perfectly at these levels, while still keeping it relatively quiet.

Keep in mind that I've been driving solely on the crappy California 91 octane pump gas.

While driving back to Norcal, the 400 mile trip was very enjoyable. Pushing it a little bit from time to time, it goes sideways in almost every gear at any speed.

I've only calculated the highway mpg on the way back, and it went down to 18mpg. (not from the crappy onboard computer, but calculated by actual distance / gallons of gas I put in afterwards).

All in all, I'm happy with the car. It's fully in your control how you want it to behave, but it can get away from you a bit if you don't respect it.

 

Glad to see your enjoying the car. Sucks that its overheating in stop and go traffic though, do you have the rear coolant mod?

 

yes I do, but it's not overheating too much right now...the temps are still significantly lower than what ppl see at the track. It's a bigger displacement now, so the heat is expected.

I have the pathfinder mod, intercooler, oil cooler, tranny cooler, and a Koyo radiator. So pretty maxed out on coolant mods.

 

+1

Are you running the 52mm thick core Koyo rad?
LA traffic in 90+ weather is bear on any engine.

 

Yes, but the thick APS intercooler is in the way...lol...

 

I can only imagine what it's like to drive that beast...

 

I realize this is a bit off topic and I appologize for that, but do you know what this 4.2 delivers in HP as an NA install?

 

nitrouz thanks for the thread

this maybe is a stupid question, but do you have a stock thermostat, high pressure radiator cap, vented hood, and jethot coated manifolds? (maybe the APS ones come coated? I dunno off hand)

what brand of coolant or water-coolant mixture are you running? Are you running anything like waterwetter?

what brand oil are you using?


do you recall if it was very hot outside?

sitting in rush hour traffic when it's hot outside I've noticed brings my coolant and oil temps up around 210-220 if rush hour is pretty bad. I'd assume with sleaves that the coolant temps would be slightly worse than an unsleaved block, but some people have said the sleaves actually improve cooling, but I don't know if I understand how


probably no one knows yet because there's only a couple out there. I think it'd add 40-45 tq at the wheels to the earlier VQ35DE up to about 6000 rpms, then drop to about 35-40 tq at the wheels at redline

 

With that kind of power, any plans of getting a custom final drive ratio to go lower than 3.3 ? At your power level and stroker engine, 3.1 would be really nice imo. Also, what kind of camber are you running in the rear? And wider tires in the rear would be nice

 

sorry I'm not sure as GTM has not done any N/A 4.24L builds in-house yet. There should be one coming out soon from overseas though, with the GTM 4.24L shortblock.

But as far as I can tell, even when driving out of boost, the car hauls like a V8. The torque is amazing even before hitting boost, and keep in mind this is only at 8.5:1 comp.

 

I have the stock thermostat, Nismo radiaor cap, Asuka vented CF hood, but the manifolds weren't jet hot coated...but they're wrapped in heat wrap.

I'm not running the waterwetter yet. No clue what that is...care to enlighten me?

I'm still running non-synthetic oil. Will be swapping out soon to Motul 300V 15W50.

And yes it was very hot outside...very hot to a point where I could be topless and sweating.

Thanks for the comments sentry.

 

No plans for a different FD as of yet. I actually like how it is right now, because I usually drive in very low rpms when daily driving, and the 3.3FD mates well to my driving habits right now.

My rear camber is at -2.2 degrees. That's as close to 0 as possible without using camber arms since my car is lowered. I would love a wider rear, but it wouldn't fit with these wheel offsets.

 

WaterWetter®


WaterWetter® is a unique wetting agent for cooling systems which reduces coolant temperatures by as much as 30ºF. This liquid product can be used to provide rust and corrosion protection in plain water for racing engines, which provides much better heat transfer properties than glycol-based antifreeze. Or it can be added to new or used antifreeze to improve the heat transfer of ethylene and propylene glycol systems. Designed for modern aluminum, cast iron, copper, brass and bronze systems. Compatible with all antifreezes, including the latest long-life variations.

Redline makes it...

 

waterwetter is a product made by redline that supposivly helps bring coolant temps down. Some people disagree that it actually does though. If it doesn't get below freezing temps that often where you live, you might consider making the coolant-water ratio more in favor of water - like 25/75% with distilled water. You can use use a turkey baster or whatever to suck out the coolant from the reservoir tank and replace it with distilled water and let the system mix them together as the car heats up and cycles it


Your car is awesome, but the dynochart won't make it very fast without good traction

-2.2 camber is probably way too much for that kinda power. At the point you're at, you'd probably wanna run like -1. I'd be more concerned with trying to get traction than having better corner handling. You might need some SPC toe bolts along with camber arms.

Everyone is going to hang me for saying this, but if you switched to a TH400 3 speed auto transmission, your car would become seriously faster than it currently is, and less chance you'll snap an axle if you did use some sticky tires

Sounds like you have some aggressive wheel offsets. If you really want good traction you're probably going to have to come to terms with changing your wheels to something with better offsets for really wide tires

thanks again for reporting on how the stroker kit has been working out

 

thanks guys for the waterwetter explainations.

sentry: I'm looking at different camber options right now, to see what I can do to make it closer to 0.

The TH400 is out of the question right now though, as I want to use this as a daily driver as well.

 

it's hard to drive a car with little traction...all those power go to wast....you should get at least 295 for rear ...should be ok

 

well it still has MOST of the traction available.

I know a lot of people say more power = waste, but I honestly don't think so. When you get used to driving a car with power > traction limitations, you start "squeezing" the throttle at the threshold of breaking traction. It's actually still pretty fast..just can't floor it all the way like N/A that's all.

 

Wait untill rain season, you'll have so much more fune.

even with N/a engine, still very easy to lose traction

 

as another option, you can always consider getting a seperate car for daily driving that'd get better than 18mpg on the highway. Then you can pull out all the stops with the Z and focus on making it perform it's absolute best

I'd assume with a car like that, when you want to drive it, you want to DRIVE it, not cruise the highway in it on your way to work putting wasted miles on your $13k+ engine


The TH400 IMO is the best option for your car because like you said, shifting is tricky because of the accelleration, and having to shift 4 times vs 2 times in the quarter mile is time wasted shifting and the shorter gearing will just make traction worse. The auto will nail the shift point each time even with 850+whp. 1st gear will take you to 60mph@7000 rpms, 2nd will take you to 110mph, 3rd will take you to 162.

You'd get more traction, more consistent shifts, less shifting, no clutch to wear out with huge amounts of torque, less chance of snapping an axle which isn't cheap to fix (would negate highway mpg with the 6 speed manual) it'd be a piece of cake to drive around town

the only disadvantage would be you don't have an overdrive gear for driving on the highway in. So other than highway mpg and it not being a manual anymore, there's no real downside

 

Have you considered switching intercoolers? I know you are making a lot of power with tons of air flow and high boost but I wonder if the 5" thick core is REALLY needed at the point you are at right now. Assuming you need it perhaps its time for some better flowing fans if you don't have them already. Some Flex-a-Lite slim lines or Spal fans would pull more CFM. If you add an HKS Fan Controller you could also lower the turn on temp for the fans and run both of them at high speed when they come on. It should help some.