Before I get a lecture about speed endangerment. I don't always do it, and I'm well aware of the consequences.

Once in awhile I like to push my car to the max speed. Giving the time on desolate road stretch I'll go for it.

My question is the IS250 AWD is rated at 130 MPH.

Now in normal auto mode I burn through all the gears to redline only to reach 6TH gear maxed out at 120 MPH. From there on out it's already at redline.

For me to hit the 130 MPH mark. I have to be in manual, and have ECT power on. At which I hit 130 MPH in 5TH at 5000 RPMs.

In other cars that I've owned (GS400). I could easily bring it up to 130 MPH with out running out of gears in normal auto.

Just trying to understand the whole situation.

I'm on stock wheel set up as well. 17x8 225 -45-17 square setup.

 

6th gear is overdrive. It's not meant for top speed. It's designed to keep RPM's as low as possible at highway speed for fuel efficiency. While most cars will hit their top speed in the highest gear, it's obviously not the right combination with this car at 205hp and AWD to achieve it.

 

I've never seen the number for 250 as far as the electronic limit. The 350 limits at 142 or their abouts. But ya, the frontal area and aero drag kill both machines. Lower gears near RL is your only hope.

That said, at WOT I'm 99% certain the transmission Torque Converter will not Lock so you have a lot of slippage. Check this out!!!

I threw your tire data in into my gear ratio calculator and get the following:
225/45R17 = 24.97"
Axle = 4.10:1
At 6,400 RPM, with NO trans slip (1st#) and with 20% slip 2nd#.
1st - 33, 26
2nd - 57, 45
3rd - 83, 66
4th - 115, 93
5th - 161, 129
6th - 198, 158

I don't recall the 350's actual RPM but 5th gear maxed at the control limit of 142. With the tune it would be interesting to see 4th gears limit.

 

Last two are if you spin it a bit more. Which usually result in more drivetrain loss. Hence last one at 25% loss.

Looks like so! If we had the manual trans you could really see the engine simply loose the aero drag battle.
Like my 600cc street bike. It makes 104hp at a stellar 49 ft/tq. It tops at 137mph from all the drag in 5th gear. 6th is even slower.

 

Thank you sir.

 

NP.... a factor that is in error is that the losses go up with the load. It is not by any means fixed as shown above. An example is the hypoid gear set in the rear diff. It induces more loss as the load increases. And because of the mechanical advantage of gears 1 - 3 the torque converter is very likely slipping more in 4 - 6 too.
There is a 6 mile stretch along the river bank where the interstate is divided and it has only 2 lanes. As its built over water there is no place to hide so testing is pretty safe in all regards. The 350 is pretty stable over 1xx. It was much fun from a dig.

Be safe!
When is the diff supposed to arrive?

 

Yeah I feel you it is fun until you end up splattered like a bug.

Yeah here in my area all the freeways have new pavement. Five lanes depending on the area. There is two stretches where I can open it up luckily for me.

Since I have the car really braced up. Just point and shoot it will go straight. I don't think I would try it with out suspension reinforcements. It was very sloppy with the stock steering ecu as well.


As for the diff no ETA yet for shipping. It's in a city 4 hrs away so it should be overnight when it does.

Still debating to upgrade the subframe, and pinion bushings.

 

Abstract but if you logged this data, you could see the loss due to slippage...

 

There's an electric limit somewhere right after the needle passes 140mph. Didn't feel like a fuel cut, more like timing retard, but either way the little squirrels in the 4GR still got a little more crazy in them when the nanny steps in. This was years ago on factory gearing, I think topping 5th out, then getting couple hundred RPM out of OD when it slows you down. On the 4.10 gears with 25.6" tires, topping OD out is right at that cut.

The 2is is surprisingly aerodynamic.

 

The Awd is250 seems to have 4:10 gear ratio which is why it’s redlined before “top speed” awd = a little heavier so they put a lower gear to keep it kind of quick. You’d need an 8 speed trans or a little higher gear to get more top end. The 2wd has 3:73 which is perfect moderation of mid range and top end without being too high for no low end. That make sense?