DIY Engine Build - well mostly

[madjak]

A little while ago I started the process of building a new engine from scratch, with the end target for this engine to be a high reving Rotrex'ed monster in the range of 400+whp. The theory is to do as much of the machining as possible myself in my workshop. Instead of paying someone to do the work, I'm going to buy the tools and do it myself! Plus I'm going to be eco friendly and use as many recycled parts as possible.

I have access to some decent tools, such as a high school hobby lathe, a Chinese vertical mill, a small hobby CNC machine and various other workshop tools. My skills aren't in machining, however I have played around with lots of things in the past. Nothing a bit of youtube and google can't teach me anyway. There are a few areas I'll avoid, including welding aluminium and machining bearing surfaces... but pretty much everything else I'll tackle.

WARNING: This is going to be a long build process and thread given I've already been on it now for 6 months so I'm guessing at another 12-24 months. It's being done in my spare time with new tools supplied as birthday or christmas gifts. Plus as everyone knows parts of this build are expensive and will need to wait until I have spare funds (which already go to my current race car as a priority).

[madjak]

PART 1 - The Engine

I picked up a dead NA8 engine that had done a big end bearing from someone on gumtree. It was 100% free so that's my starting point. The crank was cactus, but I have a spare good crank on the shelf already. The head is a BP-05 which doesn't flow so great due to the lower position of the intake ports but it's the same as my current N/A race head which means all my intake, sensors and accessories etc will just bolt right up. Plus I'm going to port it anyway so this starting point isn't a big issue. Given the power my BP-05 N/A race head makes they can't be that bad.

I don't want to touch my existing engine, as it's kind of special so I'm starting again to build an entire spare long block.

Target build is as follows:

Bottom end:

• DIY sump baffle
• DIY Lightweight crank
• Forged Rods (ebay special?)
• 10.5:1 84mm Wiseco Pistons
• DIY EWP

BP05 head with:

• SR20DE valves (around 1.75mm oversize)
• SuBs (maybe DIY modified HLA)
• High lift 275 degree cam, maybe 285?
• Valve springs from my existing head (I'll upgrade the other head)
• CNC machined combustion chamber - deshrouded valves, hand polished surface
• DIY Hand ported intake and exhaust ports
• DIY Throat boring (for oversized valves)
• DIY 3 or 5 angle valve seats
• Install new bronze valve guides (bore and taper them myself)
• DIY Head shave to raise compression to around 12.5:1

Intake:

• Skunk 2 intake (existing)
• S90 throttle body (existing)
• Rotrex C38-74

Exhaust:

• 4:1 Large diameter headers (existing)
• 3" Exhaust (Existing)

Of this list, the only things I'll really need to buy are the Rods, Pistons, Cams, valve guides and of course the Rotrex and it's required accessories. Everything else will be recycled or close to free. The first stage with be an N/A engine, with the F/I coming as a second stage.

The general theory of this build is to push the power (and so torque) up high in the revs so that it's transmission friendly. It's going to be pushing past 8200 rpm and hopefully generating 400+whp whilst doing it. This engine will be built specifically for my track car so there is no need for it to be fuel efficient, quiet or run nice below 4500. In fact with a Rotrex and some decent cam overlap this thing will be feral. With the high compression and high boost it's going to be run solely on E85.

To achieve the power level I'm designing it around a larger than standard Rotrex. Why a Rotrex? Well i makes a nice linear power curve, which means easy to drive at the limit. It also generates a torque curve thats going be transmission friendly. 400whp at 8200rpm is much nicer to a gearbox than 400whp at 5,500 rpm via a big turbo. Also Rotrex means instant power, less heat and fits into my existing setup better. Plus I'm a sucker for trying something that's never been done before.

I've already started on the crank and the head as some of you might have noticed from my other posts. Also just so it's clear, this is a learning process for me and I only partially know what I'm doing so if you have any feedback, please post it in this thread.

Next I'll post about how I photoscan and build a 3D model of the head so that I can CNC the combustion chambers.

[NitroDann]

Don't forget 6L/min of fuel, and the other electronics.

You'll probably want a waste gate on the cooler pipes or a custom throttle cable cam also.

Dann

[madjak]

Don't forget 6L/min of fuel, and the other electronics.

You'll probably want a waste gate on the cooler pipes or a custom throttle cable cam also.

Dann

Yeah fueling will come later. I might even go for dual pumps but that's a long way down the line. I'll need some help with the F/I side of things... I've never done it before and there is lots I don't know.

My initial ideas are to low mount the Rotrex where the alternator sits on the cold side of the engine. I think it will fit... just. I have a half width Honda radiator so the intercooler will sit next to it on the drivers side so it will get nice clean air. The Rotrex will feed straight into the bottom of the intercooler and out the top directly to the throttle. Compressor surge is a big issue so BOV / Waste Gate setup and sizing is going to be important as well as PWM control if I want it.

[smy0003]

So pumped for this!

[plohl]

Sub'd

Sent from my SM-N9005 using Tapatalk

[beavis]

You had me at hello.

[Okibi]

Sub'd

[rascal]

10.5:1 84mm Wiseco Pistons
DIY Head shave to raise compression to around 12.5:1

Any reason you went for 10.5 pistons and then shaving the head to get the desired 12.5:1 rather than higher compression pistons to start with and then less (or none?) shaving?

[NitroDann]

Generally this is to get shitloads of quench area.

Dann

[madjak]

10.5:1 84mm Wiseco Pistons
DIY Head shave to raise compression to around 12.5:1

Any reason you went for 10.5 pistons and then shaving the head to get the desired 12.5:1 rather than higher compression pistons to start with and then less (or none?) shaving?

Well a few reasons really.

It's hard to get higher than 10.5:1 pistons without going to something custom. Also any higher compression and you start getting clearance issues with the valves, plus it's very easy to deck to head to raise compression. The main reason though is my current race block uses 84mm Wiseco pistons so by duplicating that setup it means I only need to keep one set of spare rings, and the heads are interchangeable if I need.

There are a few reasons why you want high compression with a F/I engine.

• More compression means a bigger bang which applies greater force to the piston throughout the entire expansion.
• Higher compression helps push out the exhaust gasses after combustion leaving a cleaner cylinder. Because more exhaust has been pushed out, the cylinder gets more vacuum when the intake valve opens so it helps pull in the air.
• The squelch is more vigorous so the fuel mixture is more even.
• Compression also helps a turbo to spool more rapidly because the exhaust gasses are faster.
• Compression helps low boost torque.

I'm not really sure what max compression will work with E85. It depends on the cam profile, target air temp and boost levels. NitroDann probably has more experience on that.

[Ned Loh]

sub'd

curious about how you are going to do DIY valve seats?

[StillIC]

10.5:1 84mm Wiseco Pistons
.....
It's hard to get higher than 10.5:1 pistons without going to something custom. Also any higher compression and you start getting clearance issues with the valves, plus it's very easy to deck to head to raise compression. ....

No it isn't. Wossner do a 12:1 and they are available online. No extra clearance issues with valve cut outs which are included.

Also, if you can build a 400hp mechanically supercharged engine you can build a >>400hp turbocharged engine with the same basic engine parameters (fueling, air supply, compression, boost etc.), due to their higher efficiency (read lower mechanical losses).

[madjak]

Yeah you mentioned the 12:1 Wossner pistons before. Have you actually seen them? They list an OEM compression ratio of 11:1 which is obviously wrong so I doubt they are actuall 12:1.

Given there is very little clearance room on the peak of the 10.5:1 Wiseco piston to the head i can't see where the meat for the extra compression is going for 12:1. There is really only the area between the valves.

I think you'd need to double check the specs on the Wossners.

[NitroDann]

Also, if you can build a 400hp mechanically supercharged engine you can build a >>400hp turbocharged engine with the same basic engine parameters (fueling, air supply, compression, boost etc.), due to their higher efficiency (read lower mechanical losses).

Well, yeah and nah. A rotrex engine will never ever consume the same amount of air per cycle that an equivalent turbocharged engine can. So its likely that this build will not need to be as stout in any way from mechanical strength to tune quality that an equal power turbocharged engine would need.

As for compression? Ive got 12:1 motors on 25psi.

Dann