The question is stock to stock. After mods the SSEi would come out on top.

If you could launch the SSEi without spinning, the SSEi would take the hole shot due to it'* 280 lb/ft torque. Once the GXP hits it power band, I'd say around the 660' foot mark (1/8th mile), it will put the 3800 to shame.

The nature of a pushrod engine (3800) is about 75% of torque in the lower to mid RPM'*, Torque comes on hard, fades and then the HP comes on, and the overhead cam engine (NorthStar) has more of a mid range to top end RPM torque band, the Torque and HP come on at similar RPM'*.

Given Track Times I've seen, the SSEi and GXP run nearly same on the 1/4 mile unmodded. The SSEi has the edge for a couple reasons and has more wins than the GXP. It has more bottom end torque and the 4T65E seems to hook better to the pavement. We have had a GXP member actually run the 14.6 1/4 mile as Road and Track listed it new. But as a GXP driver, I can attest to the fact it is hard not to break the tires, losing time.

0-Top Speed? In a quarter mile you just come onto 3rd gear for the GXP. And it is on top of it'* game torque wise and able to break 150MPH with ease. An SSEi would have to be very beefed and the Speed Limiter removed to win this one.

The PCM on the GXP is Locked. It runs a preset program burned into ROM. To date and IMO this isn't going to change. We have had 2 separate incidences where Speed Shops have come forward to say they would be offering "something", yet never to materialize. With Variable ignition timing and more other sensor activity/input in it'* PCM than most other engines, altering the algorithm tables in place and it still having comfortable "streetability" would be a hard thing to pull off. Not being able to finetune a reset PCM has its negatives, you would be stuck with a "canned tune" unless you had a stock And modified PCM to run.

Production numbers are the key here. Approx 4400 made in the 2 year lifespan of the GXP isn't going to cause somebody to aftermarket parts for this FWD drivetrain even if you were able to alter the PCM to support them. A retune on a performance tuned engine to begin with isn't going to take you far without being able to mod the engine. Almost 7 years after they first started rolling off the assembly line, I'm not holding my breath.

I have noticed that this Comparison sounds alot like the Never ending Argument of 4 stroke vs. 2 stroke! Which is very relevant to my life and lifestyle. Me and my buddy argue all day about my 4 stroke Raptor 660R (which i guess would be the GXP, do to displacement) VS his Banshee 350 twin 2 stroke (SSEI, because of the power u get with aftermarket parts and the unbelievable amount of aftermarket parts) and they are both performance Quads made by the same company. Even though i rooting for the SSEI here.

Ya, and the funny thing here is we are talking fractions of a second and driver control/reaction for the two unmodded. And for that difference it has caused alot of flame wars here over the years. With the Former Senior Administrator Banning people that didn't think his way/opinion. I think they are both sporty, sexy, good running 4 door Mid luxury sedans. Flaming for the sake of claiming less then a second'* difference? No different than running in the Special Olympics........

IMO, I like the look of the GXP, the updated grill and tail lights, it looks cleaner to me. But, I love the tried and true 3800 Series II.

The advantage of the SSEi * weight, or lack of it. Also a supercharger ads a lot more torque. Stock for stock, your running nearly head to head, and as John mentioned, driver skill is the difference. You can throw NOS on a GXP and kick it up a notch, but so many more mods available for the SSEi simply leaves the GXP in the rear view mirror.

even after modding a SSEi i still think the GXP would hold maybe take the SSEi on top end, my brother have a heavily modded GP and going 160+km/h i was slowly walking him away..

GXP'* cant be tuned yet, and as John said i dont see that comingg anytime soon, if it comes i think making the GXP go fast wouldnt be too hard.. there are turbo kits for the STS that run the same engine as the GXP, it will take a little modification here n there but im sure at the end you will be able to install it... i mean once the PCM is unlocked, you're free to do whatever you want... which i promise i will be the 1st one to try once its unlocked lol
but my main concern, how good is the GXP tranny? is it gonna hold for some extra power?

There was a guy on w-body.com who compared the internals of 3 transmissions:

a 4T65E-HD, a 4T65E-HD built by ZZP, and a 4T80-E.

The 4T80-E in the Bonneville GXP is massively beefier than the ZZP built transmission by a ridiculous amount. I have no doubt that you can put a lot more power through a 4T80 than you could through a 4T65 any day.

IIRC they have a thread over on some forum for the LS4 powered cars, which were bolted to the 4T65E-HD. The thread was to have people post at what mileage their transmission blew. The mileage ranges from 18k to 50k.

See, I don't really care so much how fast I'm going all the time. Sometimes its about reliability. You're not going anywhere with a blown transmission. The LS4 cars are fast...for 50k miles or less, and then you're in the market for a new trans. You can find a ford 4.6 and put a supercharger on it, but its a ticking time bomb before you blow a rod. Sure you're going a lot faster than any other mustang on the road, but you won't be doing it for very long. That'* where I appreciate the Bonneville GXP. You can put your foot down all day long for 100k+ miles and have the peace of mind of knowing your transmission will take the abuse, even with nitrous. With a 4T65E, its a game of chance.

So at the end of the day, it depends on how deep your pockets are, and how much faith you have in your 4T65E. I know some LS4 w-body guys cross their fingers and sweat bullets every time they go to the track.

If I had an SSEi, I'd quickly find a way to bolt in a 4T80E. There is absolutely no denying the fact that the 4T65E is pitiful compared to the 4T80E, and we're not talking David and Goliath here.

Good Points X, and to people who have young family'* and/or need their cars to survive I want to make a clear point. The guys on this Forum that are doing the heavy Mods to their Bonnevilles mostly have the resources, money and other cars to be able to do them. If you start heavy modding, your going to break things. Very expensive things to alot of people. The going rate for a rebuilt tranny is ? $2000+. They can be had much cheaper in a salvage yard, IF you have the means and place to make a swap. It isn't a matter of if something will break, it'* a matter of when. We encourage, enjoy, and support people interested in making your cars have more "giddyup". We just ask that you weigh the options and results. I hate to think the Mod Bug bites somebody hard enough to throw caution to the wind and leave their family without transportation hard to replace.