You must have some very special mods on your 4.3. Or your friend's 4.7 isn't what it should be.

I think the 4.3 is a great car, but the difference with the 4.7 is quite significant. Ssaa77, a 4.7 Sports Pack manual is well worth trying.

 

OP was concerned with the 15-20k premium. These mods only cost 10k and the car is now at 375RWHP with the sport pack.

OP does not need to go through process of selling a car. If looking to stay in a Vantage it is an option that transforms his 4.3.

 

So you do have some very special mods then What are they (or is there a link -- I'm guessing you've discussed it previously)? I couldn't open the dyno chart -- what was the difference in power and torque after the mods?

 

So the real question is for OP... If you like the V8 vantage and want to stay in one, but you are considering the 4.7 (09+) then you must like the vantage...if so...

Is modding a 4.3 Vantage = a 4.7 Vantage?

I dunno about this engine much however I would venture to say that for the 09+ to be much better than the previous, there has to be more changes and tweaks to make it significantly better, I dunno that simply a small 0.4L of displacement alone could make that much of difference if everything else werer the same...

 

Nothing special really, just a few modifications that compliment each other nicely. I never did the dynos until half way through the mods so I may have had a stronger engine. The 200 cell cats increased 18 RWHP alone. The mods were the AM power upgrade (ECU tune, new manifold and air boxes), K&N air filters, QuickSilver Supersport exhaust, and 200 cell sport cats. The biggest change was in throttle response and the numbers back up the power gains. I feel like AM held back on the engine a bit and these tunes really leaned out the AFR.

 

Sounds like you've come up with a nice set of changes. But...

For a 4.3 to have "better low, mid and high range 'grunt'" than a properly running 4.7 you'd have to find 40 hp. That seems unlikely even with those changes, but perhaps it's possible -- if so, the "high range grunt" should be comparable to a 4.7. However, regarding low and mid range grunt, it is seriously unlikely that the modifications have increased torque by 44 lbs/ft. Prodrive's modifications were supposed to result in 425 hp, but there seems to be a fair amount of doubt about that. Regardless, even Prodrive claimed "only" 325 lbs/ft, still well short of the 4.7's 346 lbs/ft.

Better throttle response would be nice, though

 

Perhaps its possible? 303 lbs/ft at the wheels, 375 RWHP....I posted the dyno for your viewing and have the video. What is the 4.7 at the wheels?

 

As I said before, I have a hard time buying into that data Deto. If you got 375 whp after the cats and the ECU tune, what was the car before on that dyno?

Assuming around 305 whp stock (which others have reported), we're talking about an increase of 70 whp, from just cats and the ECU tune! Not even the manufacturer of the cats/tune claim that such large gains are possible. The numbers just don't add up, which makes me question the dyno calibration.

For purposes of comparison, I dynoed my 4.3L after RSC cats and ECU tune and got 330 whp after 3 runs. Assuming 305 whp stock (I didn't do a before dyno), that's only a 25 whp increase.

 

Thx again for all the input. I turn over cars quite a bit, so I'm thinking that a 15-20k premium on a 09 would actually save me money vs 10k in mods on my 07 if I turn over the car in another year. Could be wrong here, but just a thought.

I think some of the 09 interior upgrades are appealing too. But the v12 is so appealing if I can swing it. Probably would need to wait a year or so, but then again, something else might be out by then.

 

Another thought is that there have been other improvements made by Aston on the 4.7 beyond displacement and hp/torque, and the 4.7 will be a newer car too. If the price difference between the modded 4.3 and stock 4.7 is small (and I have no idea), I'd personally go with the 4.7.

 

The car has cats, ECU tune, filters and exhaust. CJ's (forum member) dynoed 358 at rear wheels without the filters. If you take his dyno, its still slightly higher than a non-modded 4.7L....while mine is higher still. I know in reading Mikes (BR) posts who designed these engines that they had 10hp tolerances.

Perhaps your 4.3L was really weak or you should have been questioning the dyno calibration at the place you went to?

The point was just that you can mod a 4.3L rather cheaply to a 4.7L performance.

OP-sorry for going off topic. If you can swing it-Go with the V12V, that is a worthwhile upgrade!!

 

Ha, I think my data is more in line than yours. Filters and exhaust are only good for 5-7 bhp each, and BR was only able to get the gains you're claiming after increasing displacement to 4.7 and doing other tweaks. Again, did you do a before dyno? While there is some variability from car to car, I'm sure you'll agree that an extra 50 hp in your car from the factory is highly unlikely.

 

Only did the dyno before the CATs, and the CATs alone added 18RWHP.

I wish I did dynos at each stage, but I guess it would be irrevelant as you would just continue to say I am making claims even though I have the data and the video and other forum members are posting similar gains.

Oh well, I notice a big difference and am very happy

 

I would definitely go with a GTR

Hope you find the car you want soon.

 

I'm glad you're happy with the power increase. I'm not calling into question your claims. I believe you when you say that the dyno spit out 375 whp. What I'm saying is that I don't believe the dyno. Those numbers appear to contradict other evidence from other owners, including me. Again, other people have dynoed their stock 4.3’s at around 305 whp. If you accept the 20% loss assumption, this synchs right up with 380 bhp. So, these are not “weak” Vantages. My car and others cars have dynoed at around 330 whp after cats and the ECU tune. This means an increase of about 25 whp.

Now, let’s assume that your car also originally had 305 whp like others have observed. If your car now does 375 whp, that’s an increase of 70 whp. That gain is significantly more than others have observed with similar mods or what RSC has suggested is possible. The cats and the ECU tune together are good for an extra 30-35 bhp, the exhaust maybe another 5-7 bhp, and the filters maybe another 5-7 bhp. So that’s an extra 40-50 bhp, which may be around 30-40 whp. That’s only about half of the gains you’ve seen from the dyno you used.

Now let’s assume that your mods increased your car’s power by about 30-40 whp. If your car now makes 375 whp, that means it originally had 335-345 whp which, again assuming 20% loss, translates to around 420-430 bhp. I think it’s unlikely that your stock 4.3L made more brake horsepower than the stock 4.7L.

In view of all of this, it appears that the simplest explanation for your high whp numbers is that the dyno is off.

I’m not trying to attack you or your car and I have no problem with a V8V having power that rivals my V12. I just think others should know before they invest in these mods that it’s unlikely that they’ll get anywhere near the 375 whp that you got from your dyno run.