I heard that the Allante 4.5s put out 200hp while the others put out 180, does that extra 20hp come from the intake manifold? Also what other things can i do to get more power out of it?
It appears that the difference in the two 4.5 engines is in the crank and pistons/rods. The Allante had Port Fuel Injection and earlier model 4.5's had throttle bodies. Which does yours have? Some of the earlier Allante's may have had different heads than the other 4.5's, but I may be wrong on that as I remember reading something on the Allantenet site about it. You may want to try the Allantenet.org site and do a search to see if you can find more information on the 4.5 engines.
I did a search as well and found that the easiest way to get some more power is to advance timing 2-3 degrees. If you get any knock, back it down a knotch and remember to use premimum fuel.
You might want to contact Chris Kucia from the Allante site as he seems to know a bit about the 4.5L. Check out his web site for some links and his email address.
http://my.core.com/~ckucia/
You might want to add a K&N filter and maybe some exhaust modifications as well.
Email Chris Kucia and ask him some questions about preformance mods for your 4.5L. Chris posts alot on the Allantenet.org site and is pretty up on engines and things that you might be interested in.
I appreciate the kind words, but I'm just more of an enthusiast. Luckily, over on the Allante board, we have a GM Engineer who hangs out. He's been a wealth of info.
The big thing is getting over the ECM. Allantes (and, I think most Cadillacs with 4.x engines) use a speed-density fuel management system. It has a crank sensor in the distributor, air pressure and temperature sensors, and throttle position sensor. Essentially, because the volume of the engine is fixed, the ECM uses that, and calculates the density of the air based on the temperature and pressure. With the air density, and volume (engine displacement), it knows how much fuel to add.
Obviously, an easy way to get more HP is to boost the displacement. Since there is parts interchangablity between 4.1/4.5/4.9 (Cadillac first bored out the 4.1, then stroked the 4.5) its relatively easy - except for the ECM which relies on the displacement in its fuel calculations. There are ways around this, but none as good as reprogramming the ECM.
Because Cadillac used a bunch of ECMS (the Allante's are different than the other models, plus other variations) and because Cadillac ECMs incorporate the onboard diagnostics capabilities, no one's invested the time to hack a Cadillac ECM (at least not that I'm aware of). If this hurdle were jumped, it would open up a small, but significant, performance opportunity. One other issue - the Northstar Cadillacs ECMs became PCMs (Powertrain as opposed to Engine Control Modules).
Another alternative would be to use another GM ECM. For me, the onboard diagnostics isn't worth giving up, especially as it would be crucial to tune the new configuration, IMHO.
Finally, you have to worry about the transaxle that the 4.x engine is attached to. Allantes have the F7, which, I believe, is a modified 440t4 (4t40). Later Cadillacs had the 4t60e/4t65e where the PCM adjusts engine power so that the transaxle doesn't grenade. Northstars have the hefty 4t80e, but even then, engine power is modulated to improve transaxle life.
Hope I'm not discouraging, but these are some of the real issues that unfortunately have made this great engine sort of fade off into the past. It's never going to make 500hp, but it definitely has some potential, if you could get around these issues.
Over on the Northstar thread they were talking about nitrous. Got me thinking - its probably the most realistic performance solution available for the 4.5, if done right.
I don't think you could do anything major, but mild nitrous at WOT would probably get you as much of a performance increase as anything you could get with larger displacement and/or a cam. Plus, you could probably get away without ECM doodling as its in open loop at WOT.
The transaxle is still an issue, I'd expect to tear up clutches, maybe that could be mitigated with a shift kit and/or heavy duty parts.
What I'm thinking, is that if you make changes that make overall engine performance increase, then you have to deal with constant hammering the transaxle, breaking the tires loose on the low end, decreased gas mileage, emissions, etc.
By using nitrous at WOT, you avoid all that - it only comes into play when you engage it. As long as you don't go overboard, the engine should hold up OK
Just did some quick research. NOS makes a std GM OEM V8 kit with special NOSZles that suround existing fuel injectors.
About $1500. 100HP increase. Only works at WOT. Can be boosted up to 300HP, but you need racing gas, timing retarding, and, potentially, forged pistons, crank, rods, etc.
