DIY Turbo Discussion greddy on a 1.8? homebrew kit?
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Am I missing anything and opinions

 
Old 09-18-2018, 03:50 AM
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Miata with 1.6 soon to have a built 1.8
Hi, maybe it's using my mobile but couldn't not find a build thread section so DIY turbo it is!

Just some advice on a few things, I'm going for 300-320hp, I have a list of items so far and I am doing it over the weekends for a winter project, I think it will be done in 8 weeks or so. The car I have gone about the right way and it already has its suspension, seats, harnesses on. bigger brakes are going on this weekend and the calipers have had all rubbers replaced with new slider pins (brakes seem important for such a hp per ton build). I am currently rebuilding a 1.8 engine which I'm going to put a mk2 head on once I find one!

Here is is a brief list of components for build, say brief as it's an outline to show supporting mods etc.

gaz pro adjustable coilovers
cobra bucket seats with 4 point harness
bigger brakes - drilled/grooved with yellow stuff pads
ati damper
kraken 3 inch exhaust
Cold side k & n filter
coolant reroute
intercooler with 2.25 piping
Megasquirt ms3
750cc injectors
performance HT leads
Iradium spark plugs
Bigger Fuel pump
Clutch up to 315 pounds of torque
11 pound flywheel
forged pistons and rods
Toyo888r 225 on 15's
6 speed from mk2.5
torsen 2 diff 3.63
oil catch can
silicone piping
engine rebuild - new gasket kit, arp studs, seals, all bearings, pistons, rods, water pump, gates belt, etc you get the idea!
Spraying mk2 head cover crackle red paint

Turbo - have not got a manifold, downpipe (shall be 3 inches) or turbo yet as really stuck between which turbo, I lean most towards efr 6258 but have seen some linear maps of gt2860 too. It's one of them decisions that's so important between how the car will drive I'm taking my time deciding (and the prices). I love the feeling of boost kicking in but don't want a car that will flip me out on every corner so that's where I mainly get stuck, I like driving country roads (why I got a miata) and being able to push out straights.
I'm in the uk so will probably use blink, mtech or skuzzle for tuning the car.

Reason I put bigger fuel pump is i need to research more into it so have not got this part, im thinking walbro 190hp.
Transmission - will I be ok with what I have at 300-320hp or will it snap in a week, I know there's the BMW upgrade but that's rather expensive.

Grip! - one of the most important things, will I grip well with 888r 225's? I'm not driving the car until it's ready to go get tuned, too many parts in and out!

What really is the difference between gripping and supporting 350-380hp than 300hp? All the work that's being done I feel some watermeth and a 6758 would touch 400hp and 6758 same cost as 6258. You see why I'm thinking so hard between turbos?? I actually want grip and would understand bigger tyres / alloys would definitely be needed to grip that!
Any advice would be appreciated, thanks.




Last edited by Kiki; 09-18-2018 at 04:01 AM.
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Old 09-18-2018, 07:05 AM
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Stay with the smaller turbo. It will make more power than those tires can hold anyway. It makes more than enough power to destroy that transmission eventually and will give you better transition in to boost.

You will want a better compound of brake pad for fade resistance if you decide to drive the car on the track. Drilled and slotted rotors are not generally of value on our cars. They create weak spots that propagate fractures when used hard on the track.

You will have great difficulty keeping the car cool at those power levels on the track. It will be fine for short blasts on the street.

Stock ignition coils will not be sufficient.
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Old 09-18-2018, 08:52 AM
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Solid build plan overall.

What compression ratio pistons? You want 8.6 pistons if using premium pump gas.

I vote for efr6258. I'm running it with a kraken setup and it's awesome sauce. I made 309hp at 17psi. Pump gas.

greg made 350hp pump gas and 415hp on e85 with a 6258, so really no bigger turbo needed.

forget 2860, it's a pig. You want the car to get exciting at 3500rpm or 4500rpm? That's the difference between the two.

your 6 speed should be fine to about 300-325hp. The closer you get to 400hp the more chance to grenade it.

I'm still on a measy 5 speed and typically have boost set to 15psi (280hp) street and 10-11psi track (250hp). Just to have some mechanical empathy for my 5 speed. Which btw is holding up like a champ.

as for wheels/tires. I have 15x9 with 225 rs4 and the grip is great. Next time I get tires, I'll probably opt for 245 rs4.
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Old 09-19-2018, 01:19 PM
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You are missing radiator ducting, copper plugs, suspension bushings, motor and diff mounts, fuel pump hardwired off battery/relay, new brake lines with centric plain rotors and good pads. Heavier flywheel like 13/14 lbs so you actually enjoy driving on the street. Welded not tapped oil drain return into pan higher than oil level in pan. Overall your car will be solid though.
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Old 09-19-2018, 02:49 PM
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Originally Posted by sixshooter View Post
Stay with the smaller turbo. It will make more power than those tires can hold anyway. It makes more than enough power to destroy that transmission eventually and will give you better transition in to boost.

You will want a better compound of brake pad for fade resistance if you decide to drive the car on the track. Drilled and slotted rotors are not generally of value on our cars. They create weak spots that propagate fractures when used hard on the track.

You will have great difficulty keeping the car cool at those power levels on the track. It will be fine for short blasts on the street.

Stock ignition coils will not be sufficient.

any transmissions that wont be in the 2-3k that can handle it well on the street? mine is more for street use than anything.
i shall look at different pads once these have worn down as brand new and waiting to be used!

Thanks
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Old 09-19-2018, 03:12 PM
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borka- yeah 8:6:1, the. The more I hear efr 6258 the more I fancy it haha!
Tyres I will have to bump them up a size but like my rota alloys so much.

brainzata- yeah a few bits were missed out of that list like suspension brake lines already done, poly bushes shall go on. Not all of the list was a this is what I'm thinking of some I have already bought and engine still being stripped on weekends.
flywheel would a 11 pound flywheel really be that difficult to drive?
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Old 09-19-2018, 03:12 PM
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With regard to Transmissions you really only got three reasonable choices. A Miata 5-speed which is good for around 250 horsepower, a Miata 6-speed which can get you into 300 horsepower range, and the BMW trans swap at $4k.
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Old 09-19-2018, 03:24 PM
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Originally Posted by Kiki View Post
would a 11 pound flywheel really be that difficult to drive?
No, I found my 10 pound flywheel just as easy to drive as stock. That was a Flyin Miata Happy Meal with 10.3 lb flywheel.
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Old 09-19-2018, 03:33 PM
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Originally Posted by brainzata View Post
You are missing radiator ducting, copper plugs, suspension bushings, motor and diff mounts, fuel pump hardwired off battery/relay, new brake lines with centric plain rotors and good pads. Heavier flywheel like 13/14 lbs so you actually enjoy driving on the street. Welded not tapped oil drain return into pan higher than oil level in pan. Overall your car will be solid though.
I have a 8lb flywheel with a SuperMiata 4 puck and dont mind it one bit....
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Old 09-19-2018, 04:56 PM
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I'd look for 1000cc injectors with that power goal in mind. The 750s should get you there, but if you go E85 or if you end up wanting to turn it up anymore you'll just be swapping them out.

Every 3.63 rearend I've seen for sale has been around double the cost of 3.90 since they're so rare by comparison. Check out FM's gear calculator and take note of how close those 2 ratios really are. I'd definitely prefer the 3.63's, but the difference in cost just isn't justified IMO vs a 3.90. If you do look at 3.63's, take a look at doing a getrag swap too. It seems like it's not a ton more expensive, and near bulletproof in a miata. Once it's done you get tons of cheap gear ratios to choose from.

On any street class autocross tire you'll be fine traction wise in the low 300s. 1st will spin some, but it's so short that you're not there for long anyway. 2nd generally hooks up, at least in good conditions (the early part of the tire's life, warm weather, dry roads). 3rd and above have no issues at all.
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Old 09-19-2018, 06:32 PM
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I hated the shudder from take off and chatter during de-acceleration with my lightweight Aluminum Fidanza Flywheel with exedy clutch street driving(years ago). I just like more mass for smoothness.
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Old 09-20-2018, 04:36 AM
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Kiki - I see you are in the UK so there's a few things you prob need to bear in mind

E85 - I don't think there's any plans for us to get it over here, which sucks :( If you are speccing new injectors though, I'd still say get the ID1000's / ID1050Xs, no reason not to You should be able to get north of 300whp on 98/99 RON fuel though (so Shell / Tesco). Our Super Unleaded works out to be something like equivalent to 92/93 in US numbers.

BHP - everyone on here is talking power at the wheels. Everyone in the UK talks at the flywheel, so there's a significant difference

Diffs - 3.63 final drive diffs are a lot more common here (standard fitment on some mk2.5s), but 99% of them are Super Fuji, not Torsen cores, which are known to break. You can swap over a Torsen core from another ratio diff reasonably easy though.

Fuel Pump - The DW200 is supposed to be much quieter than the Walbro 255lph equivalent. There's also a lot of fake Warlbro's about so buy from a reputable vendor (not ebay etc!)

Head - if you are sourcing a head, look out for a mk2.5 (NBB) VVT one as the megasquirt can control it. mk2.5 EUDM cars get the square top manifold as well which is another thing ticked off the list.

Garrett vs. Borg Warner - there's lots of threads on here. I think the pricing in the UK is skewed differently though, BW work out more expensive compared to Garrett here. A GT2860R is about £700, EFR 6258 about £1500. Not sure what Borka has been smoking when he says that the GT2860 doesn't get exciting until 4500RPM - maybe if it's a shitty one from a 200SX, but the GT series ball bearing ones commonly used by Begi / FM spin up way quicker than that. Not as quick as an EFR though.

The new generation Garrett GTX / GTX II turbos spool up much better than the old GT series ones, but are more expensive, but pricing is closer to a BW at about £1200. Again lots of threads on here comparing - both are within the same 'ballpark' performance wise. I've got a GTX2860, but it came as part of a package - having a quick skim through Borka's dyno thread I'd say the boost vs RPM is actually very close, but it's not apples to apples as I've got a tubular manifold whereas he's got a cast one (albeit a very good one), and I'm running a lower compression ratio than him.

There's a few different options for us in the UK that the chaps in the US don't see much:

G19 : https://www.g19engineering.com/index.php?cat=41
Davefab : https://davefab.com/shop/mx5-t25-turbo-manifold-1800cc/

If I was starting again from scratch, I'd probably get a Kraken kit with the BW turbo - Kraken is in the EU so it makes life a lot easier import wise (at least for a few more months!), and it's known to work very well.

Tuning - Don't bother calling MTech. They will refuse to map your megasquirt. I think the others will be OK with it though, or dependant where you are there's plenty of other MS tuners..

Whereabouts are you in the UK?
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Old 09-20-2018, 07:53 AM
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Originally Posted by pdexta View Post
I'd look for 1000cc injectors with that power goal in mind. The 750s should get you there, but if you go E85 or if you end up wanting to turn it up anymore you'll just be swapping them out.

Every 3.63 rearend I've seen for sale has been around double the cost of 3.90 since they're so rare by comparison. Check out FM's gear calculator and take note of how close those 2 ratios really are. I'd definitely prefer the 3.63's, but the difference in cost just isn't justified IMO vs a 3.90. If you do look at 3.63's, take a look at doing a getrag swap too. It seems like it's not a ton more expensive, and near bulletproof in a miata. Once it's done you get tons of cheap gear ratios to choose from.

On any street class autocross tire you'll be fine traction wise in the low 300s. 1st will spin some, but it's so short that you're not there for long anyway. 2nd generally hooks up, at least in good conditions (the early part of the tire's life, warm weather, dry roads). 3rd and above have no issues at all.

750cc or up 👍

I already have a 3.63 diff and 6 speed to match, the list above isn't just a want list as such I already have the a bit of it, turbo, manifold, larger exhaust (currently have 2.5) is main bits I need but the turbo decision was holding them back.

Thanks for description of grip through gears there, the autocross tires can you name a few a good ones as may swap to these!
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Old 09-20-2018, 07:57 AM
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Originally Posted by jonboy View Post
Kiki - I see you are in the UK so there's a few things you prob need to bear in mind

E85 - I don't think there's any plans for us to get it over here, which sucks :( If you are speccing new injectors though, I'd still say get the ID1000's / ID1050Xs, no reason not to You should be able to get north of 300whp on 98/99 RON fuel though (so Shell / Tesco). Our Super Unleaded works out to be something like equivalent to 92/93 in US numbers.

BHP - everyone on here is talking power at the wheels. Everyone in the UK talks at the flywheel, so there's a significant difference

Diffs - 3.63 final drive diffs are a lot more common here (standard fitment on some mk2.5s), but 99% of them are Super Fuji, not Torsen cores, which are known to break. You can swap over a Torsen core from another ratio diff reasonably easy though.

Fuel Pump - The DW200 is supposed to be much quieter than the Walbro 255lph equivalent. There's also a lot of fake Warlbro's about so buy from a reputable vendor (not ebay etc!)

Head - if you are sourcing a head, look out for a mk2.5 (NBB) VVT one as the megasquirt can control it. mk2.5 EUDM cars get the square top manifold as well which is another thing ticked off the list.

Garrett vs. Borg Warner - there's lots of threads on here. I think the pricing in the UK is skewed differently though, BW work out more expensive compared to Garrett here. A GT2860R is about £700, EFR 6258 about £1500. Not sure what Borka has been smoking when he says that the GT2860 doesn't get exciting until 4500RPM - maybe if it's a shitty one from a 200SX, but the GT series ball bearing ones commonly used by Begi / FM spin up way quicker than that. Not as quick as an EFR though.

The new generation Garrett GTX / GTX II turbos spool up much better than the old GT series ones, but are more expensive, but pricing is closer to a BW at about £1200. Again lots of threads on here comparing - both are within the same 'ballpark' performance wise. I've got a GTX2860, but it came as part of a package - having a quick skim through Borka's dyno thread I'd say the boost vs RPM is actually very close, but it's not apples to apples as I've got a tubular manifold whereas he's got a cast one (albeit a very good one), and I'm running a lower compression ratio than him.

There's a few different options for us in the UK that the chaps in the US don't see much:

G19 : https://www.g19engineering.com/index.php?cat=41
Davefab : https://davefab.com/shop/mx5-t25-turbo-manifold-1800cc/

If I was starting again from scratch, I'd probably get a Kraken kit with the BW turbo - Kraken is in the EU so it makes life a lot easier import wise (at least for a few more months!), and it's known to work very well.

Tuning - Don't bother calling MTech. They will refuse to map your megasquirt. I think the others will be OK with it though, or dependant where you are there's plenty of other MS tuners..

Whereabouts are you in the UK?
thanks for long list there

shell i I was going to use as no point running a car bhp/ton on our pump gas.
The Torsen 2 3.63 I already have with a 6 speed to go with it.

i actually have a 2004 2.5 euphonic vvt 146bhp, so could use the engine out of that but was going to sell that car as rust is appearing and I like the mk1 more.

Fuel pump i will look into thanks. I do plan on using a kraken mani,downpipe and maybe get the kit with exhaust too for 999. Davefab I thought were quite expensive to be fair.

I've done probably about 48 hours worth of research so far for this car! The price between the Borg and the Garrett is something in the decision as could get polybushed all round, exterior done and other bits for the the price difference haha! Don't want to get a Garrett and be like should of went for efr like many are saying.

im south east so skuzzle are closest to me!



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Old 09-20-2018, 08:05 AM
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Originally Posted by Kiki View Post
Thanks for description of grip through gears there, the autocross tires can you name a few a good ones as may swap to these!
The US gets a much better selection of tyres than we do - for 15s once you go over 205 width the choice gets pretty limiting - mainly 225/45s - R888s and some of the trackday special brands like Dmack. I'm running 205/50R15 Federal 595RSRs and they grip pretty well in all conditions and aren't crazy expensive..
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Old 09-20-2018, 08:16 AM
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Originally Posted by jonboy View Post
The US gets a much better selection of tyres than we do - for 15s once you go over 205 width the choice gets pretty limiting - mainly 225/45s - R888s and some of the trackday special brands like Dmack. I'm running 205/50R15 Federal 595RSRs and they grip pretty well in all conditions and aren't crazy expensive..

r888s 225 cost 450 here, family member works in a garage so can get a little off and fitted for free so that helps! I like my alloys a lot and feel they suit car well so don't fancy changing if didn't need too, they need a clean mind!
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Old 09-20-2018, 10:06 AM
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Has there ever been anyone dissatisfied with an EFR? Should make decision easier.
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Old 09-20-2018, 11:54 AM
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Originally Posted by jonboy View Post
Not sure what Borka has been smoking when he says that the GT2860 doesn't get exciting until 4500RPM
watch this video closely, ideally pause it and move the time slider little by little. this is a 2nd gear pull. (i know i know, not ideal to build boost) but you can still see the turbo is very late to the party.
This is a BEGI S5 turbo setup, a gt2860r with a T3 exhaust housing, with a begi cast manifold with Tial EWG set to 8-9 psi spring only pressure.

I am sure a GTX on a good tubular manifold and good flowing exhaust will behave much better. but this is my personal experience with a crappy BEGI setup.


here is a pic of this setup:
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Old 09-20-2018, 12:13 PM
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Originally Posted by borka View Post
watch this video closely, ideally pause it and move the time slider little by little. this is a 2nd gear pull. (i know i know, not ideal to build boost) but you can still see the turbo is very late to the party.
This is a BEGI S5 turbo setup, a gt2860r with a T3 exhaust housing, with a begi cast manifold with Tial EWG set to 8-9 psi spring only pressure.

I am sure a GTX on a good tubular manifold and good flowing exhaust will behave much better. but this is my personal experience with a crappy BEGI setup.

https://www.youtube.com/watch?v=8gmsWiF2Hvw

here is a pic of this setup:

i see what you mean, definitely want quicker spool!
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Old 09-20-2018, 12:16 PM
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My previous setup was a Begi cast manifold, IWG GT2860RS (0.64A/R), FM Elbow and a 3" exhaust - it used to get going way before your setup did. It didn't spool as well as my current setup, but it was on boost by low 2000s RPM and making a decent level of boost by 3000. The current owner of the kit has just had it dyno'd so if I remember I'll ask him for stats..

But anyway - sorry for the thread hijack Moral of the story - don't get a BEGI kit. Just buy the EFR
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