Post by
tloof »
https://forums.nicoclub.com/tloof-u11109.html
Fri Dec 08, 2006 4:27 pm
Soon2drag93,
No, there are no stock pulleys from ANY vehicle that will work...you have to have a custom crank pulley machined for this application like i did. I would't up the compression any at all over the stock 9.2 ratio, because with the extra SC boost any added compression will make it tough to prevent detonation! Headers would be good, but I doubt that changing the cams is worthwhile since you will want to maintain more midrange power off boost during cruise conditions in order to keep the fuel efficiency decent. As long as the boost level is kept below 7 psig no internal work is required on these engines.
Hardbody silvia,
I was discussing this same gear ratio issue with another guy within the 720 community that swapped a KA24de into his Hardbody 4x4 truck, and the bad news is that when I went back and looked at all the available OD gear set combinations for the FS5W71 trannys it turns out that the best ratio that is even possible with the 4x4 gear set you have is only a 0.813 ratio (this is achieved by using the 24/45 tooth OD set from a 4x4 version FS5W71B tranny out of the "B" version tranny that comes in the 720 4x4 truck). The stock Hardbody 4x4 tranny has a 0.821 OD ratio that is achieved with a 21/39 tooth OD set which happens to also be the exact same tooth combination that is used in the 240SX (and that same OD set creates a 0.759 OD ratio in a 2wd tranny that has the 3.321 1st gear). Unfortunately, only a 2wd tranny can achieve such a low OD ratio as the 0.759 or 0.7515 that those two gear sets provide (the 4wd tranny is limited to the 0.813 or 0.821 combinations). You are best to just live with the stock 0.821 OD ratio you already have.
Now, the stock differential gear ratio that is used in the 4 cyl model Hardbody truck is 4.375, so I think it will be best that you change out to a lower differential ratio of 4.625 and NOT the 4.9 that comes in the Xterra. Since the Hardbody & Pathfinder rear housings are the H233B type that have 31 spline axles vs the 33 splines on the Xterra, then that is another reason to stick with using a 4.625 ratio setup from a Pathfinder (this will also keep your final drive ratio in OD to the equivalent of 3.8 vs 4.02 if the Xterra's 4.9 gears are used). The H233B rear housing only requires that the center section be changed out when making a gear change; however, the entire front R180a housing will have to be changed to a R200a from a Pathfinder or a V6 Hardbody truck in order to upgrade to the 4.625 gears (the R200a is a direct bolt-in in place of the R180a and is much stronger!).
At 65 mph using 30” tall tires (which is typical for a 4x4 Hardbody truck) and the 4.625 gear set your engine will be turning 2765 rpm when in 5th gear (that is with the stock 0.821 OD ratio you currently have). As a comparison, at 65 mph in 5th gear the engine in my 2wd 720 is turning at 2586 rpm (this is with the 235/60-15 tires, 4.111 rear gear, and 0.7515 OD ratio I have installed). As you can see you will be running about 7% higher in cruise rpm than I am and thus will suffer slightly worse fuel mileage, but the engine rpm will be slightly higher in its power band and thus should easily go up steeper roads when cruising at 65 mph than mine will. You will have a much lower 1st gear than I do for improved offroad traction though (just for a good low gear comparison, every 1000 engine rpm will move my 2wd 720 combination 500.2 ft in 1st gear vs 426.1 ft for a 4.625 geared 4x4 Hardbody in 1st gear…so that gives close to a 15% lower 1st gear combo in 4x4 high range and of course you still have an additional gear reduction available when in 4x4 low range that my 2wd 720 doesn’t have).
Just for the record, your current 4.375 gear combination should cause the engine to run at 2616 rpm when in 5th gear at 65 mph, and would net 450.5 ft traveled for every 1000 engine rpm’s in 1st gear (which is about 1% more rpm than mine in cruise and a 11% lower 1st gear combo than mine). Also, if you were to change out to the Xterra 4.9 gear ratio, then your engine would run at 2930 rpm in 5th gear at 65 mph, and would net 402.2 ft traveled for every 1000 engine rpm’s in 1st gear (which is about 14% more rpm than mine in cruise and a 20% lower 1st gear combo than mine). All of the 1st gear calculations above are based on the fact that the Hardbody 4x4 tranny has a 3.985 1st gear vs the 3.592 that the Frontier 4x4 tranny uses.
Yuu have to change the pistons on the KA24e engine to de pistons if you want to change out to a de head, or you will end up with well over a 11.3 compression ratio...and that won't work worth a damn on the street in NA form (much less if a SC'er is added with boost).
Yes, your '95 240SX MAF will work with a '98 240SX ECU, but you really want to use a '96 240SX ECU since JWT will only reprogram that version for a boosted engine and not the '97-'98 model ECU's (I don't know why for sure, but while the '96-'98 model 240SX's are really the same mechanically, Nissan did change a few on the wire positions around in the ECU connector and JWT must not want to go thru flip flopping them around...instead they say to use a '96 ECU on the '97 & '98 models after you personally change the required wire positions within the harness). Of course you are only upgrading a '97 Hardbody, so using a '96 ECU will be no big deal anyway since you have to rewire some of the harness regardless.
the custom inlet duct I mentioned is what I had to make for my conversion, and what has to basically be done for any KAde conversion into the Hardbody or 720 trucks!