Re: Project Crossfire - a Rotrex Supercharged Limited!
Ok, so I’ve gathered some good information for a short case study. Actually, I had done a lot of the homework early on and spent some time referring back to my notes to refresh my memory. Additionally, I spent a fair amount of time on new searches looking for updates/better information.
First, I wanted to address the introduction of the manual transmission into this discussion. The manual transmission is similar in some ways but much different in others. As a matter of fact, the manual transmission is so different for the purposes of this discussion it only serves to confuse the issue. i.e. among many, many other things, you can easily change clutches in a manual to prevent slippage up to a point before other things start to break. Unlike an automatic where the clutches are internal to the transmission and aren't something that you can simply "replace" over a Saturday afternoon in your garage unless you are a transmission tech.
The real truth here is that this seems to be relatively uncharted territory with the 330. The 580 on the other hand (in the SRT-6) seems to have a much larger group that has modded cars on the track and thus a larger pool of experience from which to garner information. From what I’ve “read”, guys have definitely seen a 30%-35% intermittent increase in power without a short to mid term failure. However, one guy at that rating went down one pulley size and the estimated increase of 50-60 RWTQ broke the proverbial camels back. Under what exact conditions, I don’t know, but similar examples are out there for all to read. To each his own as to how it is interpreted.
I think the real answer to the question of what level of power increase will our tranny survive and for how long is “it remains to be seen”. The 30%-35% momentary rule does seem like a fairly common story, but again, there are multiple factors to consider as I laid out previously that can change things either way.
That said, if we apply those numbers to Lantanas situation, it shows that he fits right in that same window. If he is currently making 330 ft/lbs and we plug that into the numbers, this is how it looks:
NA = NAG1 W5A330 - Constant Torque Rating - 330 NM = 243 ft/lbs
243*1.35 = Momentary Rating of 328 ft/lbs = right at the momentary limit of this transmission
Combined with his S4’s, one might say that he could last quite a while considering what I know about that tire. The S4 is a nice tire, but it is also an Ultra High Performance "All Season" radial and not what I mean by getting serious about putting power down. Not that Lantana isn’t “serious” but the S4 doesn't rise to the level of which I was speaking. In fact, the S4 isn't even an Ultra high performance "Summer" tire. Personally, I've run all sorts of tires on my Spyder in the pursuit of traction for straight line and cornering and this is a tire about which I can speak from personal experience.
Very quickly, I remember the S4s as having a nice strong sidewall for cornering BUT they also quickly turned to butter with my turbo. I lived in KY at the time and I would swear they had salted the roads or something in the middle of the summer with those tires! I sold those things off quickly and tried a few others including Kumho and BFGoodrich. The BF Goodrich KDW2s in particular were far superior for straight line but had a softer sidewall. However, the difference in straight line was so astounding. I gave up the sidewall in favor of acceleration and stuck with the KDW2s. They also weren't the stickiest tires I ever ran but they ranked among my favorite for an all around tire once I moved back to Houston due to their wet weather traction.
The point however, is that the grip between just these two tires alone was incredible and we are not even talking about a drag radial but a slightly different class of street tire. In fact, the UTQG rating of the S4 and the KDW2 is only 100 (300-400) but that alone equates to not only a difference in traction but also in stress to the driveline components.
As traction increases, so does the stress to the components of an automatic transmission. The easiest way to sum it up is that you can potentially live with a little more power and a little less traction or the inverse; a little less power and little more traction. The tricky part is finding the right mix for the long-term and we have yet to have someone fully explore this with the 330, especially at the track.
It will definitely be interesting to see how this all pans out. Personally, I would love to be able to sell the 580 I bought and turn a profit versus having to complete one more project on my car before driving it hard!!
I'll see if I can find it, but I could swear I saw a thread where someone was talking about rebuilding the 330 to a 580. I want to say that he was saying the case could be machined to accept the additional set of clutch plates or other.