gmaslin

@drftnmaz Thanks for your input. The turbo I was planning on using is the G2.5-550. Taking @Yowzers advice, an inline setup: 1. would start spooling the turbo at 2500rpm because of the increased exhaust pressure from the S/C AND 2. make the clutch off of the S/C at 5500rpm the exact point where the turbo kicks in. Is there a way to feather the clutch off in the 5000-6000 rpm range? This would help the transition between the two chargers and flatten the torque curve?

@ajg193 Post some close up photos and provide an honest use history. @Honda Ass Dragger You sound like you know more about the DIG-T-R than I do, so I guess it'll be a trifle for you to tell us what they changed on the stock engine. I don't know exactly what they did but your last post implies you could enlighten me 8^)

@00quattro00 At 1200 kilo and 400whp from this tiny terror, you're looking at 3kilo/hp. How is that in any way inadequate to drive the car?

@00quattro00 I don't know why you're assuming the gearing will need replacement. It depends upon which car it goes into. Keeping torque below 250ft-lbs saves having to upgrade the rear which I've had to do with LS swaps, this kit will be an overall better bang for the buck than anything out there if I can get it to work as planned. @cletus That was not a built from scratch engine but a bored out Nissan HR12xxx triple with a new head. Losing the S/C got that engine down to a remarkable 40kilo. That engine used battery power to make the low end instead of the S/C. My approach is more wholistic and lighter overall when you include the battery pack 8^)

@Roman Yes, good point about the rods and pins but remember the DIG-T-R got 283 ft-lbs at 7.5k on the clock, possibly with a stock bottom. The three cylinder profile makes for a short, stout crank and I will probably try using the stock bottom on first try. If the build survives the dyno I figure it'll run well enough. The S/C will start phasing out @4500 and be completely off @6000. I haven't decided on how to achieve this yet so any suggestions here will be valuable. In full load mode, I will probably be running E98 but I was hoping for a flex fuel build. @Yowzer I've done a few LS swaps but fell in love with the concept of big power and moderate torque from a tiny lightweight engine. The Miller cycle is ECU selectable and if I'm clever about it, I can find a use for it. It looks like the stock roots blower makes 6psi, that should be fine for any pairing layout with a T/C. @Dudley Would you link me to the 4K and cam parts you would use? @kpr At 10.5K, I can be happy with ~220ft-lbs. That seems like an acceptible load for this engine. @00quattro00 I'm looking at building a bunch of these as a kit. The total weight is likely to be <70kilo so I can imagine owners of older Holdens, BMW's and Passats being interested in it, hence the 3000lb reference.

@Roman The engine block has micro polished cylinders and should rev nicely. The DIG-T-R ran it at 7500 in an endurance application. In my opinion, this engine will rev to 11k smoothly. @Yowzer Using a "normal" cam makes 93 pump gas an improbability given the outcome I desire. Remember, this is for a do anything engine, I don't want to sacrifice the good engineering on the low end just to make peak power. There may be a way to use the variable expansion even in the turbo band as a knock or low octane control or possibly a low load cruise mode. As long as they don't get in the way, options are usually a good thing. I may up needing a custom cam anyway if the stock valve apertures are a problem but having two or more profiles to work with is not a bad thing. @00quattro00 I don't consider 40 ft-lbs of torque drivable on cars that may approach 3000lbs. That may be fine on a Miata but not on a salon/sedan. The engine needs help down low. The S/C works adequately for that and you're not paying for it. What's not to like?

@00quattro00 You could compound trubo but why would you have to if the S/C is boosting the bottom? How much intake aperture do you need to get 400whp worth of air into the cylinder with a net PR of 2.8? 3.0? 3.2? The DIG-T-R had a different head than the stock HR12DDR but the same physics apply. I suspect the stock head is up to the task but the calculations asked for on the aperture will firm up my suspicions 8^)

@Roman For pure racing applications I agree with you. There's no need for the added weight and complexity of twin charging but a street car/weekend oval racer is a different story. A tiny engine like the HR12DDR that could make >400whp, be usable in traffic AND be a retrofit in just about anything would make it competitve with anything on the market. Imagine this engine in a classic Miata or an MR2!

I was inspired by this thread and was hoping to continue that topic with what the ten years since have taught us. The DIG-T-R took a stock 3 cylinder Nissan block and got 283ft-lbs out of it with just a turbo. Those engines are plentiful in junkyards with superchargers already on them so what would it be like to add a turbo to give it the top end it's badly missing? The engine is smooth enough to run to 10K so 400whp seems possible to me in a twin charge scenario, any thoughts?