Forged pistons & turbo lag reduction
 

I have a 1997 miata 1.8L & I plan to get a Garrett GT2860 from BEGI, I plan to run it at it's full potential (12psi) but talking to a specialist he mentioned that the turbo is a bit too big so there would be some turbo lag & I was thinking of purchasing CP forged pistons 84mm 9:1 compression set, I already bought a lightweight flywheel & lightweight crank pulley, what do you guys think? Is CP forged pistons a good brand? (Btw this is gonna be my daily car I plan to race it at least 20% of the time) Is increasing the bore size gonna help? Any other ways to reduce turbo lag?

I think you have no idea what you're doing.


but I'll be nice and help you anyway:
to reduce turbo lag you want to run a properly sized turbo and have the least amount of restriction in the exhaust and charge air path. Properly sized turbo is the smallest turbo that will reach your hp and tq goals, and least restriction means good hotside parts and good charge side path, intercooler flow, and IM flow.

Before you make n00b mistakes with a build/setup, I suggest doing way more research.

PS: sure, overboring and running bigger pistons will get you to 1.9L, and will help, but not nearly as much as what I mentioned above.

It's all in your plans and how much power you want. You mentioned a GT2860 at 12psi, which should be around 250whp. If that's your power goal, you'd be better off with a GT2560 that's easily capable of that power and will spool a good bit faster.

If you want to push the power a little higher, toward 300whp, then the GT2860 or GT2871 and a built motor is probably a better option.

Also, these are death to miatas. Make sure you research real well before you put it on and destroy your oil pump.

Man, you guys are getting soft in your old age! Giving good advice, with no insults?

OP, you hit the jackpot of people in a good mood for some reason... take their advice as a gift from the gods!

Keith

It'll do more than that on a BP, sir.

Too big for... what? Turbo is fine. :)

Not much.

Replace with Supertech 8.6:1 for pump gas goodness.

Good!

Bad.


Yes. Buy Supertechs anyways.

Not really.

Good tune. Good hot side. Efficient intercooler setup. Picking the correct turbo for your goals/needs, etc etc etc

lol @ "full potential" of a 2860 being 12 psi.

You sir need a 2554 or 2560.

I'd say those are both too big to be limited at 12psi on a BP. :giggle:

Somewhere, Corky and StealthNB are jizzing over that wastegate reference port.

:bowrofl:

yes yes and yes to concealer's answer, much props

Eh the turbo on my Fiesta isn't much bigger than that and it hits 21psi. 1.0L FTW

waitwaitwait... the stock 1.0 ecoboost 3 cyl is at 21 psi?

That's idiotic. lol

Yup I think it is limited to 18 or so in 1st through 3rd gears and 21 in 4th and 5th.

Just waiting for the warranty to run out so I can strap on a GT2554 and swap it into a Miata!

I second Ed. What are you talking about? Proof plz.

This thread is now about 21 psi tiny turbos, not a noob that is going "ALLOFIT" 12 psi 2860.

Did the OP ever state his peak power goals? Without that we can't give a real answer on turbo sizing.

Or, he could mention his high load [4th and 5th gear] boost threshold RPM requests, and then from there end up with whatever power at the top end.

The new 1.0 Ecoboost motor that's an option in the Fiesta. Runs lots 'o' boosto.

New cars run lots of boost. I think even the new Elantra Turbo is knocking on the door to 20psi.

http://www.nytimes.com/2014/08/03/au...view.html?_r=0

20psi, sorry, it appears I was incorrect.

I need this for my leaf blower

Here's the Fiesta turbo with a quarter on the compressor for comparison:

https://www.miataturbo.net/attachmen...ine=1410474533

I learnted the other daay that 20psi does not equal 20psi :cry:

However the idea of this thing maxed out on a log manifold and a msm intercooler would be 'fun'. Or even possibly eco friendly with a similar motor build on a bp. :drool: :party:

Well since I get annoyed every time someone uses "turbo lag", here is a clarification:

Turbo lag is something from the 70's and 80's. Most turbos today will have no lag. Lag is by definition when you are at an rpm that the turbo can make 10psi of boost, you step on the throttle and it takes a certain amount of time to get to 10psi. That time is turbo lag.

Now what you are talking about is boost threshold. That's the point in the RPM range where the turbo is making usable boost pressure.

Ding ding ding, school is done!
Now go buy an EFR, run ALLOFIT and blow that bugger up!

^EFR Post. My car still has turbo lag. Not much, but some for sure.

^Just turn that ALS on... haha

Some people run 3071/3076/3582 turbo's on these dinky BP's, so yeah turbo lag is still there ;)

Its more like spin lag. From the time you step on it to the time you're trying to steer the car backwards - spin lag

:party:

:confused::nuts:

How many turbo vehicles have you owned? This is not an accurate statement at all. My compound turbo cummins diesel still had lag and that was with a stock turbo feeding the big one.

This thread is about to turn even more fun, isn't it?

Sarcasm, see my noob post count. :loser:

Diesel is a different beast! Most diesels in stock form have huge lag due to small/restrictive exhaust system. Change that and most if not all of the lag is gone.

I have owned 7 cars in different forms, most above 350hp. Built and have helped built over 30 cars in race and street mode. Don't even remember how many I have tuned (over 50).

Even concealer's gt2554 car has lag. We measured it on the datalog, it was like .25 seconds :party:

Yeah no, modern turbos still have lag. There's a perceivable throttle delay even on the best garrett setup I've driven (FM stroker with disco potato). Its nearly inperceivable on my car with the efr, its still there but its at about the same level as some of the more throttle laggy N/A engines. If they made a 2560 sized efr it would be so short it would not be noticeable by human beings.

This is also known as "an eternity" on The Internet.

Was that at like 2000 rpms? I would figure that little baby 2554 would at least do better than that at higher rpms.

Haha I don't remember, I was a lazy POS and the logs are still sitting on my laptop. But I think it was at least above 3000rpm in 4th gear. That was from vac to the full 12psi the wastegate was set for, and remember wastegate only. It was still hauling even before it got to full boost.

I think it was rolling into it from coasting around 50mph in 4th.

When i'm actually driving it in the correct gear, there's pretty much no lag that is noticeable by a human. And i still have work to do optimizing it. Like Steve said, it's just on wastegate, and i have a small exhaust leak to take care of, 3" downpipe to go on, and i've been too lazy to get VICS hooked up and working.

I'll probably just chip away at it over the winter at this point. The pile of parts to install is growing.


Steve, you need to check out Keith (Twodoor)'s setup. It's hilariously gutsy in any gear. Because gearing.

Haha I bet it is crazy, especially compared to the fiesta I'm DDing now, as the NYT writer said the gears are so far apart they need counseling.

hahaha this is funny $hit! 0.25 seconds... haha
Maybe y'all need some VTEC! That will hit quick yo...

If you guys haven't driven an old 911 turbo, you should. Now that's lag. You get on the throttle mid corner hoping by the time you are hitting the exit you have boost!

Well if you were waiting for boost, wouldn't that actually be a threshold issue, not lag? :rofl::fawk::giggle:

No for realz, 70's turbo cars, well above the boost threshold, its kind of like punch it and pray that in a couple seconds (well it feels like a couple seconds) when the turbo actually spins up that you're straight enough that it doesnt snap sideways.

This is at like 6000rpm, they are pretty odd! :vash2::dealwithit:

I know this... i was making fun of the maybe intentional omission of "full" before boost.

You guys ruin everything. :rofl:

oh.

Which is exactly what we had to do with the greddy setup on the 1.6 when we got the car. After changing the intake piping and the entire exhaust from the head back to dumping right after the drivers seat, we only had to floor 2/3 of the way through the corner. Still sucked. It's fixed now though.;)

Yes, the wrong size turbo or issues with the system will cause lag. The main reason for the diesels lag as I mentioned. Most diesels will get more power/torque and most likely better fuel milage just upgrading exhaust to a bigger/free-flowing system. Not sure what the restrictions are that makes the car makers put crappy systems on. Most likely noise.

Had massive free flowing exhaust on my truck. Laaaaaaaaaged anyway. Unless I could brake to build boost, I would always loose the jump or hole shot........and then smile as I powered past my competitor.

I'm going to be at Cozzolino Motorsports (SE Indianapolis) around noon Saturday to dyno the car. Need to make sure I am not running too much boost :) My goal at this point is to make the most power I can while not going more than around 230 to 240 torque at the wheels. According to "virtual dyno" I am there... but I need a real dynojet to back that up before I trust it.

Keith

PS: Dynoing in 5th just seams weird!

This is off the line?

Or from a roll. Which was lag.;)

boost threshold hahaha

Some of the old Chrysler K-cars were really unresponsive with their old T3 turbos. A buddy had a little convertible that you could stomp the throttle and have time to say "wait for it" before it would make power and torque steer you towards the ditch!

Well at least the K-cars you could disconnect the wastegate and make some few infinite-PSI runs down the track! K-vans are nice sleepers haha

Having taken a ride in Ben's car this inspired me to do a highway data log for lag documentation. On my GT2860R doing a steady 80 mph on the highway in 6th gear (about 4300 RPM, well above boost threshold) from going WOT to boost hitting 9.5 psi was .366 seconds, (this is where my wastegate starts to open) and another 3.44 seconds to hit set pressure of 11.5 psi at .73 seconds after going WOT... but that is relying on boost creep to get from 9.5 psi to 11.5 psi.

I will have dyno sheets up in my build thread soon, just have to re-size and post them :D Then it is off to the 1/4 mile track Sunday.

Keith