Jump to content
SAU Community

Recommended Posts

Hey guys I'm starting a twin cam RB30 build; picking up a S2 block this weekend with 240,000kms on it. I'm not sure if it's ever been opened or if the motor was swapped at any time, but 240 was on the tacho of the VL it came out of.

I plan to fit the RB25det neo head with an MLS gasket.

Seeing as I'm going to be running full time e85, what CR do you think I should aim for? I believe somewhere between 9.0-9.5:1 would be ideal. I don't plan to exceed 20psi on a hypergear 21u highflow IWG.

I also plan to use the stock pistons and rods. But I plan on fitting fresh piston rings and giving the bore a quick hone. I also want to check bearings for abnormal wear but I'm not sure whether to just swap them all out and call it a day. Oil pump will be coming from a twin cam motor. Are the DE oil pumps the same as the DET models? And is it worth fitting a crank collar for 95% street use? None of this is set in stone so if you think I should hunt around for a lower KM's engine and leave it untouched please weigh in!

Any input or suggestions would be welcomed. I'll be posting photos etc as the build progesses and I'm really looking forward to getting started. thanks guys

At those sort of kms, I'd be getting the bores checked. They will most likely be mushroomed.

Also, why that turbo? There are much better options out there. The kando range are cheap and brilliant.

Facts are few on the ground re compression ratios - nobody seems to actually measure them. If you are going to stick with stock pistons and put a Neo head on top then that doesn't really leave you much ability to affect the outcome but hopefully it will be nearer 9:1 than 8:1

After 240,000km I would be inclined to do bearings and if you are not going to replace big end bolts you should probably use a 6,500 rev limit.

Mine is a cheapo job - rings, bearings and big end bolts (no balancing) and with stock pistons probably some where around 8:1 (less than ideal). I have an N1 pump and have been revving it to 7000 for about 3 years.

The turbo is on my 25 at the moment. I think its a good option for response and if it means I won't have to spin the absolute shit out of the unbalanced 30 bottom end then that's a bonus too. If I was changing turbo I'd look at something a fair bit bigger, maybe towards SS3-4 territory seeing as 3L +VCT will help with off boost driveability.

anyway as far as the bores go, If they are mushroomed does that mean I need to have the block bored to 86.5? If that's the case I might as well throw the block away and look for another with decent bores. Hmm making me think that I should probably look for a lower KMs RB30 to start with..

Facts are few on the ground re compression ratios - nobody seems to actually measure them. If you are going to stick with stock pistons and put a Neo head on top then that doesn't really leave you much ability to affect the outcome but hopefully it will be nearer 9:1 than 8:1

After 240,000km I would be inclined to do bearings and if you are not going to replace big end bolts you should probably use a 6,500 rev limit.

Mine is a cheapo job - rings, bearings and big end bolts (no balancing) and with stock pistons probably some where around 8:1 (less than ideal). I have an N1 pump and have been revving it to 7000 for about 3 years.

Did you use the R33 head? Also did you get the head or deck skimmed? or just clean it up and slap it together? how much power are you making and do you think I should buy ARP headstuds? Did you change all the bottom end bolts including rod bolts and I forget the name of the other but the bolts that hold the big end bearing caps down too? thanks

I'd consult with Stao about his recommendations for turbo. The 3 litre will require a fair bit more turbine capacity otherwise it will choke. You've got to let those gases out and get the engine breathing especially if you plan on pushing 20psi boost into it.

Decent quality cast pistons won't cost much and will be more than adequate for street use. Get the block bored .020" over and be happy that you aren't using old slugs that are fatigued.

If you are 100% committed to E85 then you could probably use a thin head gasket to bump CR up a touch. Bob's suggestion is good; you could physically measure the chamber volume and cylinder volume at BDC. Then you work out what HG you want. 9.5:1 is right up there but shouldn't be a problem with E85 if it's tuned right.

FWIW

I'm running BP98 with somewhere around 9:1. Off boost response is fantastic (~230RWKW @ 4000RPM) with a GT3076R (0.82 A/R) and no VCT. Dyno sheet is in the RB30 dyno thread.

E85 + NEO Head + VCT + 9:1 + Static CR + similar sized turbo would make a weapon of a street car.

Edited by R32Abuser

Thanks guys. Yeah I'm thinking the 21U is a bit small. It is pushing around 300rwkw on 20psi on the 25det with the stock manifold and IWG; it seems to nose over the top of the power curve towards 7000-7100ish. I'm happy for now not revving that hard.

I'll have to inspect the block once I've pulled it apart before I make any final decisions. Thanks for the help guys

Did you use the R33 head? Also did you get the head or deck skimmed? or just clean it up and slap it together? how much power are you making and do you think I should buy ARP headstuds? Did you change all the bottom end bolts including rod bolts and I forget the name of the other but the bolts that hold the big end bearing caps down too? thanks

Yes R33 head - just cleaned up. Making just over 300AWKW. Stock head bolts and main bearing cap bolts just better rod bolts. You'll do better with a Neo head and suitable turbo.

Im gonna get the neo head skimmed for hopefully 9.5-1 on E85, why fall short if its a street engine, need all that bottom/mid range poke,

how much should be skimmed to have 9.5ish on E85 ???? guessing a couple of thou would be a good thing?

Edited by AngryRB

9.5 Should be a walk in the park for E85, there are engines out there running more compression and boost with that fuel.

You will need to calculate your compression ratio, take some measurements of your deck height, piston dome volume, head gasket thickness and cc your combustion chambers, then just do the maths.

If you are using a standard RB30 NA buttom end with a Rb25det R33 engine head it should give you an compression ratio of 8.3:1, roughly 135psi per CYC. I think its a good compression ratio. With the ignition angles, its about where the engine produced the best torque, with E85 fuel and lower compression it allows you to have it set at optimum angles and run heaps of boost without pining.

Then you might want to go for an .82 turbine housing for the high flow, or some thing like an ATR45SS-1 that can supporting around 450rwkws mark.

If you are using a standard RB30 NA buttom end with a Rb25det R33 engine head it should give you an compression ratio of 8.3:1, roughly 135psi per CYC. I think its a good compression ratio. With the ignition angles, its about where the engine produced the best torque, with E85 fuel and lower compression it allows you to have it set at optimum angles and run heaps of boost without pining.

Then you might want to go for an .82 turbine housing for the high flow, or some thing like an ATR45SS-1 that can supporting around 450rwkws mark.

This is what I have and its far too low (compressions are in the range 130 - 132 psi). OP is going to use the Neo head which will give better CR (and be better all round).

That's the idea. I'm aware my turbo is too small to be efficient in the top end but I'll be happy with a midrange monster at the moment.

I figure I want the engine done properly and get the car running and tuned nicely before I go thinking of turbo upgrades. I could swap out the turbo now but I'd rather do it properly with a highmount manifold from ETM or 6boost with an external gate + a turbo like the FP3582 or something from the hypergear SS range; haven't decided yet. One thing at a time.

And who knows, this new highflow profile flows really well in the top end on my 25 so I think it will surpass expectations. If I end up with the same top end power figure as I've got now at lower RPM with a high~ish comp 3L + VCT then I have nothing to complain about! In 4th gear currently it builds 20psi by 3400rpm on a flat road with minor boost leaks. Can't imagine what it would be like with the planned setup

Okay I can't actually move forward with this build until I sell the superkart. I've got to move on this trailer and kart for garage space and now that the 25 is running again I'm not rushed for this build.

If anyone knows anyone that is interested in a superkart that is capable of getting into the 61 second laps at Wakefield let me know. I've personally done 1:02.3 but that was it's only race event ever and there's still more fine tuning to do.

post-113447-0-07537600-1401856259_thumb.jpg

post-113447-0-35777900-1401856288_thumb.jpg

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Surely somebody has one in VIC. Have you asked at any shops?  Is this the yearly inspection or did you get a canary?
    • This is where I share pain with you, @Duncan. The move to change so many cooling system pieces to plastic is a killer! Plastic end tanks and a few plastic hose flanges on my car's fail after so little time.  Curious about the need for a bigger rad, is that just for long sessions in the summer or because the car generally needs more cooling?
    • So, that is it! It is a pretty expensive process with the ATF costing 50-100 per 5 litres, and a mechanic will probably charge plenty because they don't want to do it. Still, considering how dirty my fluid was at 120,000klm I think it would be worth doing more like every 80,000 to keep the trans happy, they are very expensive to replace. The job is not that hard if you have the specialist tools so you can save a bit of money and do it yourself!
    • OK, onto filling. So I don't really have any pics, but will describe the process as best I can. The USDM workshop manual also covers it from TM-285 onwards. First, make sure the drain plug (17mm) is snug. Not too tight yet because it is coming off again. Note it does have a copper washer that you could replace or anneal (heat up with a blow torch) to seal nicely. Remove the fill plug, which has an inhex (I think it was 6mm but didn't check). Then, screw in the fill fitting, making sure it has a suitable o-ring (mine came without but I think it is meant to be supplied). It is important that you only screw it in hand tight. I didn't get a good pic of it, but the fill plug leads to a tube about 70mm long inside the transmission. This sets the factory level for fluid in the trans (above the join line for the pan!) and will take about 3l to fill. You then need to connect your fluid pump to the fitting via a hose, and pump in whatever amount of fluid you removed (maybe 3 litres, in my case 7 litres). If you put in more than 3l, it will spill out when you remove the fitting, so do quickly and with a drain pan underneath. Once you have pumped in the required amount of clean ATF, you start the engine and run it for 3 minutes to let the fluid circulate. Don't run it longer and if possible check the fluid temp is under 40oC (Ecutek shows Auto Trans Fluid temp now, or you could use an infrared temp gun on the bottom of the pan). The manual stresses the bit about fluid temperature because it expands when hot an might result in an underfil. So from here, the factory manual says to do the "spill and fill" again, and I did. That is, put an oil pan under the drain plug and undo it with a 17mm spanner, then watch your expensive fluid fall back out again, you should get about 3 litres.  Then, put the drain plug back in, pump 3 litres back in through the fill plug with the fitting and pump, disconnect the fill fitting and replace the fill plug, start the car and run for another 3 minutes (making sure the temp is still under 40oC). The manual then asks for a 3rd "spill and fill" just like above. I also did that and so had put 13l in by now.  This time they want you to keep the engine running and run the transmission through R and D (I hope the wheels are still off the ground!) for a while, and allow the trans temp to get to 40oC, then engine off. Finally, back under the car and undo the fill plug to let the overfill drain out; it will stop running when fluid is at the top of the levelling tube. According to the factory, that is job done! Post that, I reconnected the fill fitting and pumped in an extra 0.5l. AMS says 1.5l overfill is safe, but I started with less to see how it goes, I will add another 1.0 litres later if I'm still not happy with the hot shifts.
    • OK, so regardless of whether you did Step 1 - Spill Step 2 - Trans pan removal Step 3 - TCM removal we are on to the clean and refill. First, have a good look at the oil pan. While you might see dirty oil and some carbony build up (I did), what you don't want to see is any metal particles on the magnets, or sparkles in the oil (thankfully not). Give it all a good clean, particularly the magnets, and put the new gasket on if you have one (or, just cross your fingers) Replacement of the Valve body (if you removed it) is the "reverse of assembly". Thread the electrical socket back up through the trans case, hold the valve body up and put in the bolts you removed, with the correct lengths in the correct locations Torque for the bolts in 8Nm only so I hope you have that torque wrench handy (it feels really loose). Plug the output speed sensor back in and clip the wiring into the 2 clips, replace the spring clip on the TCM socket and plug it back into the car loom. For the pan, the workshop manual states the following order: Again, the torque is 8Nm only.
×
×
  • Create New...