Sequential Gearbox, Compound Turbo/NOS/VVT 1.6 1991 NA MX5 - aka Financial DISASTER
Thought my incoming build will interest some peeps here, and figure it's about time I start compiling some information on my current build and future plans.
I also hope to get some feedback (incoming "y no 1.8") from all of you on anything you think I am planning on doing that is egregiously wrong. Yes that you read that right, a sequentially shifted, compound turbo VVT 1.6 with NOS, I won't go 1.8, I like making things harder for myself, it's part of the fun for me, this is why I'm retaining at least P/S and probably A/C too. NOS is dependent on turbo sizing requirements. Current setup is a pretty basic GT2554R running somewhere in the vicinity of 200 with a slightly crap DIY log-manifold, 5 speed gearbox, coil-overs and 1.6 VLSD. Did the turbo conversion in about 5 12 hour days over last Christmas, then the car spent many many months getting painted, and now it's been sitting under a cover for winter (leaky top + **** weather). The car is in a good state now, yes I will probably blow my diff soon, a torsen is on the cards currently, they don't pop up very often here. I'll get some photos collated and uploaded over the next week or two once it passes certification. ECU: I run a Speeduino ECU, I like open-source things, it isn't perfect but I want some specific behavior for launch control, and flatshift, I will be modifying the code for these functions to suit my purposes. Same goes for Sequential Shift-Cut and dual EBC control for the compound turbo setup. This will mean running a second map sensor, I may instead just go for electronic control on only the secondary turbo. Now to the fun stuff. See, my mind regularly wanders and I find my self getting more financially draining ideas, I now think I may have a sickness as I have begun planning out the Compound Turbo setup. I hope to have this ready around late next year, my current "I WANT" number is 600HP, I don't see this being impossible. I will probably eventually want more. This is very much in the planning phase so specifics will change, in saying that, there is only a very very very small chance that I do not go ahead with pretty much the title, I have dangerous levels of determination for this stuff. My near term intention is to get a second running 1.6 in good health (probably from a NB 1.6 as we have plenty of those here in NZ and I prefer the true crank trigger as opposed to CAS), get it on the stand and start disassembling. Get the ZL-VE head and mock things up, prepare everything for machining and assemble the block empty. Then get it on a stand and start mocking up manifolds, turbo placement, etc. My current thoughts and issues I can think of:
Some questions I've got: 1. I hate being spoonfed, but I'm struggling to find consistent information about damper options for a 1.6, can't get a clear answer on whether there is an ATI SuperDamper option for 1.6 engines or if it is only for later model 1.6 etc. If anyone has some info on that, I would greatly appreciated it. 2. What blindingly obvious mistakes do you all think I'm making. 3. Do you love or hate this idea, or somewhere in-between? /this is pretty badly formatted, I will fix it eventually. |
Ditch the VVT, it isn't worth it.
turbo compressors are rated by air-mass and pressure ratio Look into pat's various threads for clues on challenges associated with a too-small turbo stage in a compound setup Godlesscommie runs a compound turbo with success I believe Compound isn't the secret to high hp, for that you want a large single turbo, see Derek's build |
Originally Posted by Ted75zcar
(Post 1624925)
Ditch the VVT, it isn't worth it.
turbo compressors are rated by air-mass and pressure ratio Look into pat's various threads for clues on challenges associated with a too-small turbo stage in a compound setup Godlesscommie runs a compound turbo with success I believe Compound isn't the secret to high hp, for that you want a large single turbo, see Derek's build Going compound mostly so I can have a wider power band with the small turbo, although I love my mates big turbo build I'm not a fan of the high boost threshold. |
Issue is that both compressors and both hotsides need to flow the peak hp airmass in a compound setup. You can do a twin or compound twin hybrid and bypass a limiting compressor in certain operating conditions, but complexity goes up quick when you do this.
A T25/28 IWG for example will not bypass 600hp worth of exhaust gas. You will certainly need to have an external wastegate there. A 400hp compressor will choke at 600hp, it simply can't move that much airmass. |
Originally Posted by Ted75zcar
(Post 1624929)
Issue is that both compressors and both hotsides need to flow the peak hp airmass in a compound setup. You can do a twin or compound twin hybrid and bypass a limiting compressor in certain operating conditions, but complexity goes up quick when you do this.
A T25/28 IWG for example will not bypass 600hp worth of exhaust gas. You will certainly need to have an external wastegate there. A 400hp compressor will choke at 600hp, it simply can't move that much airmass. Still need to figure out how the whole corrected airflow stuff works on compressor maps when feeding higher than atmosphere air into it, since in theory that should result in higher mass of air for same CFM. That is my main concern though since I really don't know yet how big my primary will need to be to not choke whilst still not spooling like crap. It very may well be that I end up having to substantially lower my end goal power wise, but I enjoy the process so we shall see. |
That is just it, for turbo compressors it is mass not CFM. A PD supercharger on the other hand is volumetric so it is CFM not mass. If I squeeze 1 lb of air into half the volume I get a PR of 2 and a CFM of 0.5x, but the mass is the same.
600hp of air has a given mass, let's say 60lbs/min for simplicity. It doesn't matter if that is at an absolute PR of 4 with a relative PR of 2, the mass is what matters. Off the cuff, I suspect the smallest compressor you could use in something like this for either stage would be a gt3076 or similar. Run 2 sequential 3076s at a PR of 2.25 each stage, and you get a a total PR of ~5, but they both must compress the same air mass, or 60lbs per minute. Also keep in mind that hotsides act in much the same way, the PRs compound across each stage. |
Originally Posted by Ted75zcar
(Post 1624931)
That is just it, for turbo compressors it is mass not CFM. A PD supercharger on the other hand is volumetric so it is CFM not mass. If I squeeze 1 lb of air into half the volume I get a PR of 2 and a CFM of 0.5x, but the mass is the same.
600hp of air has a given mass, let's say 60lbs/min for simplicity. It doesn't matter if that is at an absolute PR of 4 with a relative PR of 2, the mass is what matters. Off the cuff, I suspect the smallest compressor you could use in something like this for either stage would be a gt3076 or similar. Run 2 sequential 3076s at a PR of 2.25 each stage, and you get a a total PR of ~5, but they both must compress the same air mass, or 60lbs per minute. Also keep in mind that hotsides act in much the same way, the PRs compound across each stage. Or am I missunderstanding here? |
Yeah, I think you are misunderstanding a bit, but it is also possible the misunderstanding is on my side. Compound turbo is super common for diesel, maybe there are some resources available there that will provide clarity.
Edit: just looked at a couple of diesel oriented pages and it would appear as if you can get a higher air mass through a compressor in a compound configuration, so who knows? |
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