Johnny Rad

My '02 GS430 and '08 GX470 have nearly the same power characteristics despite the GX's larger V8 (4.7L versus 4.3L). Someone told me it was towing-related, but the numbers don't seem to support it.

* 2002 GS430: 300hp @ 5600rpm and 325 ft/lbs @ 3400rpm
* Revised GS430 in '04 or '05: 290hp @ 5600rpm and 319 ft/lbs @ 3400rpm
* 2008 GX470: 263hp @ 5400rpm and 323 ft/lbs @ 3400rpm

What gives? What am I missing?!

mann777

There is lack of aero-dynamics on the SUV compared to the sedans. There is huge coefficient drags on the SUVs compared to the sedans.Large SUVs are very convenient for families, vacations and grocery lugging, but the necessary box-like design brings with it certain compromises. Simply put, the bulkier or less streamlined a vehicle is, the greater force will be exerted upon it from air-drag as it pushes through (against) the air during acceleration. All things being equal, this cuts into fuel efficiency. It also translates to comparatively poor handling at high speeds when, in the case of an emergency, a sharp turn of the wheel is required to avoid hitting an on-coming object. This is not to say that SUVs are not safe, but that they are less safe in certain situations than those vehicles that are designed based primarily on car aerodynamics.

pagemaster

Not only that. I would like to add that the Toyota/Lexus SUV's weight more and use fulltime 4wd in most cases which put even more strain on the engine thus eating up horsepower. The gearing of the GS is designed for quick acceleratioin while the GX is not.

Johnny Rad

I agree folks, but that's not the question.

The larger 4.7L V8 puts out the same power as the smaller 4.3L V8. What gives with the extra .4L bringing nothing to the table power-wise?

gsobol

HP and Torque numbers can be deceiving. They don't show the whole story.

What's the compression ratio on these engines? (10.0 for GX, 10.5 for GS) What are the power curves for the engines? Red lines? The GS engine is higher revving than GX, making the top HP come in later and higher in the power curve - not ideal for the heavier truck.

Overall most sedan engines are designed with higher performance in mind. Most truck engines are designed with longevity in mind. (Yeah, I'm discounting the economy here - less variables to explain) That's why you generally have a higher displacement engine with lower rev range and lower compression in the truck. It is not uncommon for car manufacturers to have two identical engine blocks, but tweaked differently for a sedan and truck (different heads, headers, intake, injectors, ECU, etc.).

The idea is that since the truck is heavier and it's expected to do more strenuous work, you put in it an engine that can do work 'easier', with less stress on the engine components which it would allow it to last longer. That doesn't mean that 4.7 in GX will outlast 4.3 in GS. What it meas is that the 4.7 in GX will outlast 4.3 in GX.

mann777

Johhny I think your question is if that is what I understand the simple formula is
power = (torque x rpm) / 5252

at some point torque normally stops increasing but as rpm continues to rises the power will also continue to rise. If torque starts to drop slowly then the power levels off and at some point both will start to fall.
There is an inverse relationship with the Torque and Bhp.

Now coming to the specs you have mentioned on the GS Now lets take the first example
* 2002 GS430: 300hp @ 5600rpm and 325 ft/lbs @ 3400rpm
Now Enter the formula ( power = (torque x rpm) / 5252 )
For the First Part (300 x 5600 / 5252 = 319 Lbs Torque
For the 2nd Part ( 325 x 3400 /5252 = 210 Lbs Torque

* Revised GS430 in '04 or '05: 290hp @ 5600rpm and 319 ft/lbs @ 3400rpm
Now Enter the formula ( power = (torque x rpm) / 5252 )
For the First Part (290 x 5600 / 5252 = 309 Lbs Torque
For the 2nd Part ( 319 x 3400 /5252 = 206 Lbs Torque

* 2008 GX470: 263hp @ 5400rpm and 323 ft/lbs @ 3400rpm
Now Enter the formula ( power = (torque x rpm) / 5252 )
For the First Part (263 x 5400 / 5252 = 270 Lbs Torque
For the 2nd Part ( 323 x 3400 /5252 = 209 Lbs Torque

Simple dynamics - You increase Power , Torque decreases, because Torque is high at low gears in first initial move, then as you increase speed, torque is required lesser at higher speeds. I hope this enlightens you...cheers buddy

gsobol

Actually the formula is power (HP) = (approx) torque (ft lb) / 5252

You can use it to calculate how much horsepower the engine is producing at the particular rpm range providing you have the numbers for torque and rpms.

So, only calculations for the 2nd part are accurate. You just have to change the Lbs to HP.

werewolf

You're dead right about the tweaks for sedans and SUVs, Lexus GS 400/430 run tundra engines with tweaks

Johnny Rad

Thanks for the info, team. Good stuff. The "towing" thing sounds right, albeit a bit thin on the why.

Ultimately, I take it to mean that we've got loads of untapped power potential in our 4.7L V8s! Xenons won't make it faster and neither will iPod interfaces, but that's mostly what we talk about ... any ideas other than a weak-kneed CAI?!

pagemaster

There is not much more power to be found in the 4.7. When the 4.7 debuted there was not VVTi and it stayed that way for about 7 years of production. Compression was also lower than the 4.0 it was based on at 9:1. When VVTi was added the compression jumped to 10:1.

The 4.7 was designed from the beginning to be a low reving engine with high torque. It was designed to have low speed cylinder filling.

The 4.0 actually was rated at 300hp at one point with the addition of VVTi. When the 4.0 went to 4.3 the power stayed the same while fuel economy got a little better. Toyota never increased the size of the 4.0 for power but instead increased it for other reasons.

The 1998 4.0 VVTi LS400 made 290hp 300 lb ft tq
The 2002 4.3 VVTi LS430 made 290hp 325 lb ft tq
The 2005 4.7 VVTi Tundra made 282 hp and 332 lb ft tq

*all specs are before the SAE revision

gsobol

pagemaster is right. The block of the 4.7 was not designed for high performance applications. Some have tried to put a supercharger only to find their blocks cracked or worse. So not much you can do. You could put better headers and alter the exhaust. You could extrude hone your intake, ECU mods, etc. It will cost you a lot of money for a very small return - 25-50 hp (?). Nitrous is an option, but the result might be the same as the blower. I guess you could try to swap an engine from GS, LS or SC (?), no idea how this would play out, and no idea of an actual world benefits. If you have a lot of liquid cash laying around, my bank account and routing number is ..... ;-)

pagemaster

[QUOTE=gsobol;4512237]pagemaster is right. The block of the 4.7 was not designed for high performance applications. Some have tried to put a supercharger only to find their blocks cracked or worse. QUOTE]

The Lexus cars use and aluminum block. The Toyota/Lexus 4.7 use an iron block. Toyota has now moved to aluminum blocks on the 5.7 and upcoming 4.6.

Och

iTrader: (3)

[QUOTE=pagemaster;4512476]The 4.7 is an iron block?! I highly doubt it.

gsobol

No, I think pagemaster is right. It is an iron block. Which raises another question, why TRD has stopped manufacturing the superchargers for the 4.7L ?

The G Man

One engine is design for a truck, the other for a sport sedan. The 4.3L is a lot more advance than the 4.7. Size of the engine dont mean much, just look at the GS350's V6, that 3.5L makes more than 300 horsepower.