I have a 240SX with a turbocharged KA24DE. I was running a T28 from a Pulsar GTiR, with a 10 psi wastegate actuator, 550cc injectors, Z32 MAF, and a RS Enthalpy tuned ECU, all on stock internals. AIl was well and I put about 5000 miles on the setup with no issues. And then I got greedy and cheap. Greedy for more boost... and cheap so that (I'm embarrassed to say) I bought a generic boost controller off ebay. Turned out to be a leaky piece of crap, and while I intended to turn the boost up to 12-13 psi, instead it spiked over 18 psi the first time out, which was more than the stock pistons could handle. #3 and #4 = blown ringlands, at the very least... I haven't had time to investigate fully yet, all I know is when I pulled the spark plugs, those two were soaked in oil.

So the car has been sitting, as I don't have the time or money to rebuild it yet. This has been leaving me with plenty of time to think about what I want to do with the car. My ideas have ranged from rebuilding the KA as capable street motor to withstand 400 whp on a daily basis (and then running about 350 whp), to swapping a VH45DE, to completely frankensteining something. I generally tend to dream more on the realistic side of things, but the following is more on the crazy side for me.

I just recently read through all the blog posts about project spec V, and building the QR engine.

My question is this. Would it be possible to do this exact build on a longitudinal QR25 from a Frontier? There are several points of concern for me.

First, is the fully counterweighted crankshaft interchangeable between the transvers and longitudinal motors?

Second, does the longitudinal version have the same balance shaft system, and will the JWT removal kit work on the longitudinal engines as well?

Third, what are the differences between the heads? Can the spec-V valvetrain work on a Frontier QR?

Now, the reason I ask about all this is because I'm wondering how easy or difficult it would be to drop a QR25 in a 240SX. I know most people's initial thought would be "why in the world would you want to do that?" or "what in the world makes you think that would be possible?" Well, hear me out for a minute. I know full well that this would be an extremely expensive undertaking, but cost, time, and money are not my concerns at this point. This is meant to be a discussion of what it would actually take to do this.

First, what would I (ideally) like to do?

The overall build would be a QR25DET, or possibly QR25DDT (More on the DDT in a moment) in a 240SX, running a twin scroll Borg-warner EFR 6258. I want something that will be reliable as a summer daily driver, and able to withstand weekend abuse without flinching. I would want it to be very streetable with a wide powerband and 300-350 peak whp.

Second, why the QR?

1. The QR25 is the replacement for the KA & SR series motors.

2. It is lighter than both of them.

3. The long stroke will spool a turbo quickly, and have good torque characteristics, which works well for my intended goals.

Third, what makes me think it will work?

1. The QR25 is the replacment for the KA & SR motors.

2. The S-chassis car came with both the KA & SR motors.

3. The Frontier also came with the KA motor.

4. Newer Frontiers now have the QR.

So my logic is as follows: If a Frontier KA can be used in a 240SX, can a Frontier QR be used in a 240SX?

I have never heard of this being done before, and I expect it would be an expensive procedure requiring a fair amount of fabrication. That is part of the appeal to me. Not just making it work or cobbling it together, but making it look professional and oem quality. This is essentially my idea of what Nissan could build if they chose to resurrect an S-chassis car.

Now, back to the QR25DDT... the QR25DD is a direct-injected version of the QR engine that came on the JDM P12 Nissan Primera. If the transverse QR head can be made to work on a longitudinal QR, then I could use the head from the DD engine for this build. Why would I want to use direct injection, you ask? Turbocharged Direct-injected engines are storming the market. They have broad, flat torque curves, and still get decent fuel economy. I'm imagining a QR25DDT with 350 hp and 350 lb-ft of torque from 2000-5000 rpm, a similar powerband to Audi's 2.5 TFSI 5 cylinder engine. Sure, this may be a pipe dream, but I'd love to work on it and see what results could be acheived.

forget about the DD. JDM Primera parts are hard to find and harder to get. You would also have no way to tune it.

There are a lot of similarities between the longitudinal and transverse motors and a lot of differences. The cam profiles are different, the head is different due to where the coolant has to enter the head. The starter on the FWD block is transmission mounted, the RWD is block mounted.

The 2004+ ECU are OBD port laptop flash tunable now.

300whp and 300wtq is easy with a medium sized turbo, like a 50trim or a gt30. You should be able to make over 300whp with around 9psi of boost and the long stroke and big motor spins one up pretty quick.

The RWD motor has a different balance shaft setup and a stamped lower oil pan. I don't think the shafts are removable because they drive the oil pump iirc. But if that's the case you could have them turned down on a lathe.

Thanks for the the feedback.

Regarding the heads - would the FWD cams be a direct swap? I think I would use the RWD block and head, and use the FWD spec V cams, if possible, and the later spec V fully counterweighted crank, if possible. The balance shaft issue would bother me. I wish I had one of each for comparison.

Regarding the DD, I know you said forget it, it's unobtainable, and untunable... but I have to ask... even with a full standalone ECU, such as an AEM EMS, it could not be tuned?

don't go the standalone route. There are very few that will work with the drive by wire and variable intake cam timing.

The factory ECU is the way to go, no base maps to build to get it to even start, no endless dyno and street tuning. You can scratch out a very good map in an hour or so if you start with the factory maps and flash tune with UpRev's Osiris program. It has real time tuning capability, access to fuel, ignition timing, cam timing, start enrichment, k tables for injector scaling, MAF tables, throttle by wire, idle speed targets, MIL/check engine elimination, rrev and speed limits, multiple map storage and on the fly map switching, sensor and parameter logging, etc. etc. etc........ only $700 for the whole deal. You could run the car off of a Spec V ECU and maps.

The cams would drop right in and as far as I know the 8 counter weight crankshaft would too. JWT has a new HUGE camshaft out too. Don't know what you'd have to do about a flywheel, and the intake manifold for the frontier is plastic.

nissan4u.com is an online version of Nissan's FAST parts system. You can look up a lot of parts, part numbers, and compatibility on there.

I have a web site with almost every FSM ever, but I don't post it openly because I want it to stay up, so PM me if you need it.

I don't know if the DD injectors could supply the amount of fuel you'd need to run a turbo set up at 200% stock power.

Would other nissan dd injectors fit the QR DD head though? such as the R35 GT-R injectors? If so, then possibly some OEM, or even aftermarket GT-R injectors might work.

The VH45DE swap would be a lot cheaper than what your thinking about doing. Since I can't think of anyone or heard of anyone doing what you plan to do it's going to get really expensive unless you do all the work yourself.

because it's never been done, you shouldn't try it.

Because it's never been done, then I shouldn't try? That's precisely why I would want to try. It would be something new, different, and unique. At least I would find out if it actually could be done or not.

Posted By Big J on 04-08-2011 08:18 PM
because it's never been done, you shouldn't try

Please tell me where I said he shouldn't do it. I'm just pointing out the reality of it. That can make it go from a pile of parts to a car that can be driven. I'm the last person that would say you shouldn't do it because it has never been done.

 

Someone put a QR25DE into a 510

http://www.the510realm.com/viewtopic.php?f=31&t=12917

I say do it. I've got 92,000 miles on my motor now. It's been boosted for 60,000. It's been putting down over 300+ whp and almost 300 ft/lbs the whole time. EVERYTHING about the motor is stock (except injectors and turbo kit), I've never even had the valve cover off.

Mike even has a turbo QR. It makes a lot of power on not a lot of boost........... cough**cough** he needs to ship it out here so we can finish it and shake it down at Road Atlanta.