Which cylinder(s) tend to knock first?

[NismoBoyo]

After having attempted to find out which cylinders I will need to focus my knock listening on for my buddies R32 GTR, my searches have come up dry.

So I come here to inquire as to your experiences with which cylinders are more likely to knock or knock sooner or more frequently than others in high horsepower applications.

I will update this once I get a chance with the actual full build list if required but here's the basics: Built RB26 block and head, Kelford 182-C 282dur 9.2mm cams, Upgraded housing and T51R mod GTX3582R Gen 2 Billet wheel/BB, 100mil jdm intercooler, super fire coil packs, Frenchy's twin fuel hanger with dual Walbro 450s, n1 oil pump w billet gears, PRP adjustable cam gears, Nitto head oil drain, Mishimoto rad & fans, id1300cc injectors, flex fuel kit, billet fuel rail, ported stock intake manifold??(might change), can't think of anything else at this point, lmk if there's anything else. 

In addition, I was curious if the build would be better off with a Haltech or link or the many others that are slipping my mind, or is it mostly personal preference? 

 

[Duncan]

ECU really comes down to tuner preference, the general features are the same. Link will give you move $ for $ than Haltech but that is only a small part of the total cost.

No idea which cylinder knocks first, although legend has it #6 might in an rb26 due to plenum design (more air at the rear)

[NismoBoyo]

Well I'll be the one tuning so I guess that'll be up to me. And that's a very interesting tip at the end, I have always noticed that its weird how the intake manifold stays the almost the same size from cylinder 1 all the way to 6 with the stock intake manifold but on others such as the hypertune manifold it decreases I'm guessing in a hope for a velocity gain?(just recalling from memory, feel free to correct me). 

[NismoBoyo]

Also do you think we should upgrade to a hypertune or similar intake manifold or will the stock one be fine?

 

[Murray_Calavera]

This is from the Haltech Pro Plugin base map. As Duncan was saying about the #6 cylinder, hopefully this can help quantify it with some numbers. 

Haltech's individual cylinder trim start adding fuel from cylinder #4 onwards. 

 

[NismoBoyo]

Thank you for that map that make's it a lot easier to understand also is that just a weird scaling or what trim is it for?

 

[Murray_Calavera]

Copy paste from the ECU description - 

This table allows for the fuel injection timing for Injector # to be corrected. The correction is a percentage adjustment on the overall fuel timing value. 

[Dose Pipe Sutututu]

My engine builder also asked me to dial in essentially the same trim for 1, 5 and 6. when I tuned it on his dyno.

[GTSBoy]

4 hours ago, NismoBoyo said:

super fire coil packs

Don't do this. They will inevitably be shit. Replace with some modern pencil coils.

As to the standard plenum being more "same" along its length than the aftermarket ones - don't be fooled. The stock plenum is short and the last two runners are somewhat squeezed together.

[NismoBoyo]

 

1 hour ago, GTSBoy said:

Don't do this. They will inevitably be shit. Replace with some modern pencil coils.

As to the standard plenum being more "same" along its length than the aftermarket ones - don't be fooled. The stock plenum is short and the last two runners are somewhat squeezed together.

Like is the wall of the casting thicker at cyl 5&6 larger and therefore a smaller area than what it looks like? and wdym by pencil coils, unfortunately still adjusting from yank terminology or maybe I'm being stupid?

[NismoBoyo]

2 hours ago, Murray_Calavera said:

Copy paste from the ECU description - 

This table allows for the fuel injection timing for Injector # to be corrected. The correction is a percentage adjustment on the overall fuel timing value. 

That's what I was thinking, my curiosity made me ask because I was like if that's the normal fuel map it has to be some weird scaling or something.

[GTSBoy]

23 minutes ago, NismoBoyo said:

 

Like is the wall of the casting thicker at cyl 5&6 larger and therefore a smaller area than what it looks like? and wdym by pencil coils, unfortunately still adjusting from yank terminology or maybe I'm being stupid?

The stock plenum looks like this

You can clearly see that it's not just a row of 6 pipes hanging off a common log volume. The 6th runner is different - its inlet is facing the incoming flow running along the plenum itself. This was mostly to make space for the clutch master cylinder in the GTR.

As to the coils.... the stock coil format in RBs is standard fare for the 1990s. Lumpy laminated coils, either with or without inbuilt igniters (depending on vintage, and which particular engine we're talking about). The best replacements of this same type are Splitfire. They are basically exactly the same as the OEM coils. No better, not worse. All the other replacements in this stock format, which come in red, yellow and a range of other shitty colours, are all crap. Each and every one of them are bottom of the barrel cheapo Chinese copy manufacture and are barely suitable for stock engines, let alone anything that needs to punch through a dense cylinder charge.

Jump forward to more modern engines - everything from Audi R8s, other VAG products, every other Euro, all the Toyotas (Corollas, Supras, RAV4s), Nissan engines like the VQ and VR (and all the shitty 4 cylinder shockers) - they all use pencil coils. This is the new format. They're just much skinnier than the blobby old school laminated coils. Some of them, like the Corolla coils, were very cheap and much more powerful than any stock format RB coil, so we used those. Then people worked out that the Audi coils, the ones from the R35 GTR, and various others were very very powerful, and not that much more expensive. And so we use those.

For a 1000+ HP engine, you are about 500HP into the territory of needing the best coils, and not the shitty rainbow coils that you list in your OP. The most expensive part of the exercise is having to buy a "kit" to go with the coils, with appropriate stems and springs and loom/adapters to connect with. And, for an RB26, you will need to delete the igniter pack, which is not hard, just has to be done.

[joshuaho96]

These days RB26 ignitors are so expensive new that you may as well go for R35 coil conversions. All new stock ignition components are roughly comparable to an R35 coil conversion in price and that assumes you shop around and get decent prices. Deleting the ignitor is super easy. Just buy the harness adapter if your kit doesn’t come with one. It’s basically just some wires connecting the old input and output of the ignitor directly instead of putting a transistor between the two like the OEM setup. Don’t do what I’ve seen some people do and gut an old ignitor and solder wires inside it to make a cheaper version. It technically works but it’s courting disaster.

I also recommend not using a mishimoto radiator or their electric fans. The factory oil cooler dumps all of its heat into the coolant so you do need a decent radiator and fan. From the people that have raced these cars their recommendation is universally to run a factory clutch fan/shroud and a decent radiator. Keep in mind too much intercooler pressure drop will also reduce the efficacy of the radiator. 

As others have mentioned one big reason for cylinder 6 always dying first is the compromised design of the factory intake plenum. Technically I believe it’s called an intake manifold collector but that’s a lot of extra words. The runner for cylinder 6 is clearly designed to make it possible to clear the clutch master cylinder and brake booster to make it possible to pull the plenum with the engine in the car relatively simply. As a result it sits at the very end of the plenum chamber which means it’s the path of least resistance. If you compare the OEM plenum to a Nismo plenum the big change that sticks out is cylinder 6 no longer has a weird curved runner and the plenum chamber extends past the runner to make the air have to make a turn to balance the airflow a little better. On top of this most of the cylinders in that plenum have a bellmouth design to improve airflow while cylinder 6 doesn’t. 

The other problem is that cylinder 6 is the last cylinder to get coolant flow. So it’s naturally going to run hotter than others. Pretty much any time you see people post compression test numbers after blowing up an RB26 it’s cylinder 6 that looks the worst.

[Ben C34]

On 11/14/2022 at 11:28 AM, NismoBoyo said:

That's what I was thinking, my curiosity made me ask because I was like if that's the normal fuel map it has to be some weird scaling or something.

Your thread is basically asking about trim maps then you are surprised when you see one!

[NismoBoyo]

15 hours ago, joshuaho96 said:

These days RB26 ignitors are so expensive new that you may as well go for R35 coil conversions. All new stock ignition components are roughly comparable to an R35 coil conversion in price and that assumes you shop around and get decent prices. Deleting the ignitor is super easy. Just buy the harness adapter if your kit doesn’t come with one. It’s basically just some wires connecting the old input and output of the ignitor directly instead of putting a transistor between the two like the OEM setup. Don’t do what I’ve seen some people do and gut an old ignitor and solder wires inside it to make a cheaper version. It technically works but it’s courting disaster.

I also recommend not using a mishimoto radiator or their electric fans. The factory oil cooler dumps all of its heat into the coolant so you do need a decent radiator and fan. From the people that have raced these cars their recommendation is universally to run a factory clutch fan/shroud and a decent radiator. Keep in mind too much intercooler pressure drop will also reduce the efficacy of the radiator. 

As others have mentioned one big reason for cylinder 6 always dying first is the compromised design of the factory intake plenum. Technically I believe it’s called an intake manifold collector but that’s a lot of extra words. The runner for cylinder 6 is clearly designed to make it possible to clear the clutch master cylinder and brake booster to make it possible to pull the plenum with the engine in the car relatively simply. As a result it sits at the very end of the plenum chamber which means it’s the path of least resistance. If you compare the OEM plenum to a Nismo plenum the big change that sticks out is cylinder 6 no longer has a weird curved runner and the plenum chamber extends past the runner to make the air have to make a turn to balance the airflow a little better. On top of this most of the cylinders in that plenum have a bellmouth design to improve airflow while cylinder 6 doesn’t. 

The other problem is that cylinder 6 is the last cylinder to get coolant flow. So it’s naturally going to run hotter than others. Pretty much any time you see people post compression test numbers after blowing up an RB26 it’s cylinder 6 that looks the worst.

Running a HKS type-s oil cooler and the mishimoto unit we picked for cheap unused from a friend who ended up deciding to run a rear mount radiator?(can't exactly remember his setup I could be completely wrong). As well, thank you for the greater insight into the airflow and manifold design context.

13 hours ago, Ben C34 said:

Your thread is basically asking about trim maps then you are surprised when you see one!

Yea I just like to triple check to verify things because I dislike when I have to assume things, but also yea I do look kind of dumb.

[Dose Pipe Sutututu]

Mishimoto and radiator should not be used in the same sentence.

[joshuaho96]

10 hours ago, NismoBoyo said:

Running a HKS type-s oil cooler and the mishimoto unit we picked for cheap unused from a friend who ended up deciding to run a rear mount radiator?(can't exactly remember his setup I could be completely wrong). As well, thank you for the greater insight into the airflow and manifold design context.

Yea I just like to triple check to verify things because I dislike when I have to assume things, but also yea I do look kind of dumb.

The HKS type S cooler is pretty weak and you still need the factory oil heat exchanger. If you really can’t be bothered to swap back to OEM clutch fan and a nicer radiator you can see what happens but odds are you will have trouble with cooling especially if you end up in stop and go traffic on a hot day. 

[NismoBoyo]

6 hours ago, joshuaho96 said:

The HKS type S cooler is pretty weak and you still need the factory oil heat exchanger. If you really can’t be bothered to swap back to OEM clutch fan and a nicer radiator you can see what happens but odds are you will have trouble with cooling especially if you end up in stop and go traffic on a hot day. 

Do you have any recommendations for oil coolers for the r32? 

[Murray_Calavera]

7 hours ago, NismoBoyo said:

Do you have any recommendations for oil coolers for the r32? 

There isn't anything fundamentally wrong with the HKS cooler, the reason people shy away from it is the small core size. 

But at the end of the day, the size of the core you need will depend on how you use the car. If you log your oil temps on track and your oil cooler isn't keeping up, go to a bigger core/better ducting to the core. 

[joshuaho96]

18 hours ago, NismoBoyo said:

Do you have any recommendations for oil coolers for the r32? 

There’s nothing wrong with the HKS kit, people just don’t know the limitations of it. It’s designed to fit in the space that exists. You can maybe squeeze in a bit more but not much in the passenger side fender. Driver side is crammed full with intake piping and requires deleting the OEM BOVs if you want to fit another oil cooler there. The Nissan N1 factory oil cooler deletes the AC condenser to fit more area. I’ve seen some cars put the oil cooler at the bottom of the car basically right where the engine splash shield is. This lets you put in a lot more oil cooler but the risk of emptying your oil sump everywhere is pretty high.

As others have mentioned if you need more oil cooler one way to try and drop temperatures is improved ducting through the core. Air doesn’t naturally want to go through the core so improving ducting and aero does a huge amount. If you want to get fancy with it you can use 3D scanning and do some CFD to estimate where the right places are for intake and exhaust.