Qr25DE

[isoteric]

I am trying o find out if the QR25 engine will bolt up to the KA24DE Engine mounts on a stock 95 240SX SE. I am aware that it is a front wheel drive engine, but I am trying to find out just about the engine itself as well as the components and what all is aluminum and possibly if anyone knows the weight difference between the two engines. I would very much like to take the QR25 and machine it and then replace my KA24 with it. If anyone can add any input or help me on any aspect of this, it would be much appreciated.

[Aries]

turned 90°, you would need to redesign the mounts on the block itself. Otherwise, it will work, but will need a custom bellhousing on the transmission of your choice

[_dk]

it's your car, do what you want with it-

but IMO, you'd be swapping in an engine with less overall potential than the KA (not to mention how much work it'd be). wanna be unique and all-motor with a modest bump in power? i say consider an RB25DE...

[isoteric]

why do you say that motor has less overall potential? i'm just curious since it IS the NEW 4-cylinder, not to mention the immediate 15 hp and 20 lb-ft torque gains before any machining, which I was also planning on doing. I'm just curious b.c I'm trying to do as much possible research on this as I can, I would like to stick with the 4-cylinder and I would very much like to stick with the 2.4/2.5 b.c of the displacement. If I DON'T do the swap, I would be rebuildng, boring, port and polishing, and all the other little N/A goodies I could with the KA, EVENTUALLY going with a fabricated supercharger. At least that's what I would LIKE to do.. buuuuut, like I said, I'm still getting in research and just want to know all I can with everyone's opinion. Thanks.

[Evil98Silvia]

Unstable hybrids worked on a supercharger for the KA for a while, never came out though. I dont think it was very succesful

Robbie

[_dk]

why do you say that motor has less overall potential? i'm just curious since it IS the NEW 4-cylinder, not to mention the immediate 15 hp and 20 lb-ft torque gains before any machining, which I was also planning on doing.

newer does not necessarily mean better.

Quote »I'm just curious b.c I'm trying to do as much possible research on this as I can, I would like to stick with the 4-cylinder and I would very much like to stick with the 2.4/2.5 b.c of the displacement.[/quote]right there with you on that one

imo, what's wrong with that engine is that to get 2.5 liters out of it they had to use a very long stroke and comparatively short rods, which is not optimal for an inline four. after searching, i found the stroke is 100mm and the rods are 163mm, making it obvious what the ratio is; people call the KA-D a "truck motor" but in stock '91 configuration (before the gradual detuning process that every nissan seems to go through) it's more capable of power output and RPM than the QR is.

a 1.63:1 rod ratio is great for torque because the quickly-moving piston promotes better cylinder filling at low rpms, which combined with that close-ratio 6-speed makes the new v-spec a good stoplight fighter (read: they usually kept even with my stripped 160hp/2000lb gti)- but i haven't forgotten how my old '91 classics were good for 7500rpm, bone stock; & they still had enough torque that an LSD was very beneficial to them. i personally don't think a QR25 will see 7 1/2 even with a built bottom end- forged internals can only do so much against unfavorable geometry.

dave coleman mentioned fixing this problem by using a QR20 crank available from other nissans in an analysis article on the QR25, but somehow i can't see the cylinder head being THAT much better than SR or KA that i'd go through the extra expense of buying a newer QR just to take it back to two liters...

in short, that big fat displacement number the QR25 has certainly seems attractive, but attaining it required compromises that you simply don't want in a high-performance motor of any kind; a short rod ratio is bad for boost tolerance as well as RPM...

Quote »If I DON'T do the swap, I would be rebuildng, boring, port and polishing, and all the other little N/A goodies I could with the KA, EVENTUALLY going with a fabricated supercharger. At least that's what I would LIKE to do.. buuuuut, like I said, I'm still getting in research and just want to know all I can with everyone's opinion. Thanks.[/quote]i think you've got a good plan; but the few grand it'd cost to get a stock QR25 shoved in there would be better spent executing it on your KA.

[isoteric]

ok, good deal, that makes sense. thank all of you for responding and if anyone else comes across my post and has any additional info they'd like to state, it would be appreciated. Also, if anyone might know how much machining on the KA costs, i.e. the Boring and Port And Polishing as well as the rebuilding, I could use some ballpark figures so I'll have an idea of what's fair when I go prive hunting. Thanks Again.

[phoenixR34]

Well to defend the QR, I'll just make a few points..

1. It's lighter than the SR, which I'm sure the KA is heaver than the SR. Front end weight savings means you're closer to that 50/50 balance and a faster car because you're not trying to accelerate as much weight.

2. At peak, the QR make 26 more ft.lbs and 22 more HP than the KA in stock form, and at 3000rpms it makes 41 more ft.lbs and 26 more HP.

3. Dave Coleman's car with I/H/E and Cams made ~175hp at the wheels, more than a KA will make.

4. There are a few engines that have compatible parts with the QR25DE. The QR25DD has a different header (much better at that), and the QR20 parts mentioned about eariler. Nothing better than modifying a car with OEM parts!

In theory if a QR swap was simple to do and cheap, I wouldn't hesitate because I don't plan on getting crazy with modifications to my engine. If you wanted to do the same, it would be a nice option.

If you talk in terms of turocharging possibilities, maybe the QR isn't the best and neither is the KA, that's why the SR and CA exist.

However, changing to a QR engine into a 240SX sounds very complex and I don't plan on doing it anytime soon. If the KA was the best of the best, I highly doubt Nissan would have built a new engine.. I'm sure it's quite expensive to develop a new engine. People who diss the QR, just read stuff out of magazines..

[C-Kwik]

Couple of things. According to SCC, Sunbelt who is building a motor for a Speedworld Challenge V-Spec, would not push the QR past 6800 RPM. But not being able to rev really high is not necessarily a bad thing. The motor can still be tuned well within those revs.

As far as turbocharging, at last year's convention, Nissan had a turbo V-Spec there. A Nissan Engineer took off down the street with it. Looked pretty damned fast to me.

[_dk]

[quote=" phoenixR34 3. Dave Coleman's car with I/H/E and Cams made ~175hp at the wheels, more than a KA will make.[/quote]says who?

this guy didn't seem to need cams for 169whp on the motor...

wonder what a set of pdm/jwt stage 2's would have done for him had he decided not to go turbo?

Quote »People who diss the QR, just read stuff out of magazines..[/quote]that or they just don't buy into the hype...