What the Mazda RX-8 should have been (new autocross car build) - Page 46

wdc330i · 06-09-2022, 01:41 PM

Whoa. Just saw this. What a mess.

John V · 07-14-2022, 09:27 AM

The state of my short block for the past two weeks. Rings gapped, cylinders honed, measured and cleaned, bearing clearances measured. Crank, oil pump, rear main seal installed. So basically all of the time-consuming work has been done. It just needs pistons. I've been waiting on them for a month. They were supposed to ship last Friday, but the manufacturer encountered delays in final machining. Now they're supposed to ship (overnight) on Friday, to get to me on Saturday). I'm not holding my breath.

I leave for Toledo on Wednesday, with or without the car.

I'm kind of excited about this engine. It's now an Ecoboost crank (which is forged, 94mm stroke rather than the 100mm stroke of the cast 2.5 crank). Same 89mm bore, so it's now 2.34L, down from 2.49L. Pistons are now 2618 forgings, much stronger than the prior pistons. Upgraded to Ecoboost sodium-filled exhaust valves. It should make as much power as the last one. It might make a little less power from 3500-4500 RPM but I was always limiting boost at low RPM anyway since it would just knock the tires off. The shorter stroke gives me more RPM headroom. Safe upper limit should be 8500 RPM now - don't think I'll ever go there, but being able to routinely spin to 7500-7800 would be really nice.

Also new engine mounts, something I CAD'ed up and bought from SendCutSend.com, then welded up. Much nicer than my old hacked-together tubular mounts.

JV

JST · 07-14-2022, 09:52 AM

Is the block still a basic 2.5L block? And when you say eco boost, is that the 2.0 or the 2.3?

John V · 07-14-2022, 10:14 AM

It's a basic 2.5L block.

The 94mm crank is the 2.3L unit.

JST · 10-10-2022, 11:42 PM

Gordon Murray also apparently enjoys a built Duratec:

https://www.theautopian.com/mclaren-...d-masterpiece/

John V · 10-11-2022, 08:16 AM

Pretty cool, odd though that he didn't use a VVT head. That's just throwing power away for no good reason.

JST · 10-11-2022, 08:30 AM

Trying to replicate the peakier power delivery of the original? Idk, that’s the only thing I can think.

John V · 10-11-2022, 12:37 PM

A lot of people don't run VVT because their engine management solutions can't run it. But when running a factory ECU is so easy, there's really no reason to use anything else for a street car.

Nick M3 · 10-11-2022, 12:54 PM

Quote:

Originally Posted by John V

A lot of people don't run VVT because their engine management solutions can't run it. But when running a factory ECU is so easy, there's really no reason to use anything else for a street car.

I'm going to guess that it's related to the ITBs and etc.

John V · 10-11-2022, 08:16 PM

What would itbs have to do with vvt? If anything I'd want vvt more with an ITB motor

07-14-2022, 09:27 AM	#452
John V No more BMWs Join Date: Apr 2005 Carmudgeonly Ride: Ram, MS3, CX-5, RX-8 Location: Glenwood, MD Posts: 14,740	The state of my short block for the past two weeks. Rings gapped, cylinders honed, measured and cleaned, bearing clearances measured. Crank, oil pump, rear main seal installed. So basically all of the time-consuming work has been done. It just needs pistons. I've been waiting on them for a month. They were supposed to ship last Friday, but the manufacturer encountered delays in final machining. Now they're supposed to ship (overnight) on Friday, to get to me on Saturday). I'm not holding my breath. I leave for Toledo on Wednesday, with or without the car. I'm kind of excited about this engine. It's now an Ecoboost crank (which is forged, 94mm stroke rather than the 100mm stroke of the cast 2.5 crank). Same 89mm bore, so it's now 2.34L, down from 2.49L. Pistons are now 2618 forgings, much stronger than the prior pistons. Upgraded to Ecoboost sodium-filled exhaust valves. It should make as much power as the last one. It might make a little less power from 3500-4500 RPM but I was always limiting boost at low RPM anyway since it would just knock the tires off. The shorter stroke gives me more RPM headroom. Safe upper limit should be 8500 RPM now - don't think I'll ever go there, but being able to routinely spin to 7500-7800 would be really nice. Also new engine mounts, something I CAD'ed up and bought from SendCutSend.com, then welded up. Much nicer than my old hacked-together tubular mounts. JV Attached Thumbnails

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06-09-2022, 01:41 PM	#451
wdc330i dogged Join Date: Dec 2003 Carmudgeonly Ride: '22 M440 xDrive GC Posts: 12,988	Whoa. Just saw this. What a mess.

07-14-2022, 09:52 AM	#453
JST 195 Join Date: Oct 2003 Posts: 24,396	Is the block still a basic 2.5L block? And when you say eco boost, is that the 2.0 or the 2.3?

07-14-2022, 10:14 AM	#454
John V No more BMWs Join Date: Apr 2005 Carmudgeonly Ride: Ram, MS3, CX-5, RX-8 Location: Glenwood, MD Posts: 14,740	It's a basic 2.5L block. The 94mm crank is the 2.3L unit.

10-10-2022, 11:42 PM	#455
JST 195 Join Date: Oct 2003 Posts: 24,396	Gordon Murray also apparently enjoys a built Duratec: https://www.theautopian.com/mclaren-...d-masterpiece/

10-11-2022, 08:16 AM	#456
John V No more BMWs Join Date: Apr 2005 Carmudgeonly Ride: Ram, MS3, CX-5, RX-8 Location: Glenwood, MD Posts: 14,740	Pretty cool, odd though that he didn't use a VVT head. That's just throwing power away for no good reason.

10-11-2022, 08:30 AM	#457
JST 195 Join Date: Oct 2003 Posts: 24,396	Trying to replicate the peakier power delivery of the original? Idk, that’s the only thing I can think.

10-11-2022, 12:37 PM	#458
John V No more BMWs Join Date: Apr 2005 Carmudgeonly Ride: Ram, MS3, CX-5, RX-8 Location: Glenwood, MD Posts: 14,740	A lot of people don't run VVT because their engine management solutions can't run it. But when running a factory ECU is so easy, there's really no reason to use anything else for a street car.

10-11-2022, 08:16 PM	#460
John V No more BMWs Join Date: Apr 2005 Carmudgeonly Ride: Ram, MS3, CX-5, RX-8 Location: Glenwood, MD Posts: 14,740	What would itbs have to do with vvt? If anything I'd want vvt more with an ITB motor