ctxspy

iTrader: (3)

The volvo has a 2.5L 5-cylinder turbo making an unknown-to-me amount of boost.

It's rated at around 230hp and 235 lb-ft of torque. The power to weight ratio is probably similar between my two cars but the volvo has full torque at like 1500 rpm.

After driving the volvo for a few days in a row, switching to the miata feels disappointing (at least in regards to acceleration). In the Volvo a quick jab at the throttle at low RPMs creates a satisfying lurch forwards. The miata, in comparison, feels sluggish until it opens up around 3500 / 4000 rpm.

SO, to all the owners of fast miatas, what are your tips for generating more juice down low? Is a 3" exhaust a good bet, or do you reallly just need more displacement for good low end torque?

cueball1

iTrader: (13)

What turbo are you running? What exhaust? At 10psi you must be maxing out those 305's. Tune? Timing?

curly

iTrader: (25)

Should be hitting the limit of 305's at around 8psi, definitely 10 without a fuel pressure riser. What are your air/fuel ratios?

Smaller turbos are the cure if you want more power down low, but obviously you'll be sacrificing your top end powah a bit. I'm running into that problem in my Greddy setup. Great power starting as low as 2000rpm, but once it hits full boost at 4000, it just sits there at the same power/acceleration until redline. Still fast though.

ctxspy

iTrader: (3)

damnit, i wrote a whole reply and lost it.. here it goes again

I have a begi-s with gt2554 turbo. Kept the FPR with the 305s, can hit 10.0 AFR under full boost.

Fuel & Timing is tuned on the street, no dyno time.. local guy quoted me "125 for three pulls". I don't knwo if that's enough time to really do anything so i haven't gone yet

Current timing map attached, maybe that's part of it?

Oh -- my exhaust is a 2.25" stainless steel "made in china" deal w/glasspack exhaust. the cat is by magnaflow.

-Tomaj

kotomile

iTrader: (24)

More boost, bigger exhaust, tune.

ctxspy

iTrader: (3)

(just realized i forgot to attach timing map -- will get it in a minute!!)

18psi

iTrader: (76)

no offense, but if you think your volvo is fast enough to make the miata seem slow your miata must be SLOW AS *****


Generating more torque down low can to a certain point be done by retuning timing down low. opening up the breathing also helps.......or you could just get a tiny *** turbo (like the one on the volvo) and gain a **** ton of lowend/midrange at the expense of your topend

kotomile

iTrader: (24)

He already has a 2554, can't go much smaller than that, really.

ctxspy

iTrader: (3)

@18psi -- LOL no offense taken.

That's the other thing.. i've never driven a 'fast' turbo miata so i'm not sure what exactly it should feel like when set up right.

Maybe i should just bite the bullet and do a dyno run just so i know where i stand, maybe that'll give more information on what to do next/

kotomile

iTrader: (24)

I'd guess around 170-180.

18psi

iTrader: (76)

There sure is. Have you seen how small those volvo turbo's are? ESP when compared to their engine size. Put a turbo on the miata that is roughly the same ratio of turbo/engine as the audi and you'll have a shitton of torque down low/midrange. That would be fail though, since the topend would be utter **** just like it is on the volvo.


Its nice to have lowend torque on a daily driver, I know EXACTLY how OP feels.

kotomile

iTrader: (24)

Semantics, sir. There are smaller turbos, but as you said, they would be complete fail on a Miata.

sn95

iTrader: (2)

Low end torque in a 1.6L Miata costs money, how much do you want to spend??

A 2L FE3 with custom turbo manifold and BB 2560 would pull like a freight train.

The same turbo on a 1.8 BP would also have good low end.

If you want 8-10 psi boost by 2,200 RPM (and don't want to run more than 10psi), put on an Aerodyne or Aerocharger VATN turbo (don't expect it to last as long as a Garret)

If you want the best of both worlds with a 1.6L, run a compound setup with T28 sleeve turbo blowing into a supercharger.

samnavy

iTrader: (7)

Using an RRFPR with a fully tunable ECU introduces a variable that isn't needed. Sell the RRFPR and the 305's and get some RX7 550's and dial in your tune. At 10psi with the 2554r and a 2.25" exhaust, I'd say 180-190whp is about right... but you'll never know without a dyno. I don't think you'll see a huge WHP jump by switching to a 3" exhaust, but you'll see a big torque increase and probably see full boost a full 500rpm quicker. Besides a tune with bigger injectors, a bigger exhaust is what you need.

How are you tuning timing? What map are you using?

$125 for 3 pulls is a crock of ****. That's what all the Socal AWD dyno guy get because there are so few of them and they'e alway full. But a simple 2wd dyno on a mid weekday should be $50 for a set of baseline pulls or I'll just do without.

ctxspy

iTrader: (3)

samnavy, i hear you regarding the extra variable of the FPR... I"ll keep an eye out for a set of injectors and once i get them i'll do the swap and pull out the FPR... Know anyone who wants one?

I'm not really tuning my timing.. I'm sure i'll get flamed here but i just look at what everyone else is running and try to pick what seem like safe numbers.. Way back before i got my IC and megasquirt i used to get knock, so i know what it sounds like (i know there's various kinds, even inaudible).. i haven't heard anything remotely like it and i don't drive that crazy so i figure i'll be OK for now.

@sn95 - i've read enough horror stories to not consider the aerodyne.. sounds like really neat technology but i don't want the headaches. Eventually if my engine ever dies i'll consider getting a 2L if my budget permits, or at least definitely a 1.8L.

pusha

iTrader: (5)

Do you have a link to where this has been done on a 1.6?

magnamx-5

iTrader: (7)

sure if you search on m.net you will see the twincharge lunacy totally unnecessary, and overcomplicate imo.

To the OP i suggest more timeing and more boost. A properly tuned WI system will help you with both.

jayc72

iTrader: (14)

10:1 AFR isn't helping you out.

ctxspy

iTrader: (3)

jayc72 -- you're right that 10:1 is too rich, i'm just trying to make the point that I *can* hit that number.

My targets are as
11.8 @ 170kpa,
12.0 @ 150kpa,
12.8 @ 130kpa,
14.2 @ 110 kpa
14.7 @ 100 kpa-30kpa

How do you like your enthuza 3" exhaust? Did you get the regular or budget model?

-Tomaj

P.S. timing map is finally here

sn95

iTrader: (2)

Not if you really want good fuel economy, good low end torque and good high end power out of a small displacement engine; all small displacement vehicles don't weight 2,200lbs and have manual transmissions with stiff rear end gearing! Compounding requires a LOT of engineering to work properly but it will give good low end torque and high end power. If you watch the OEMs you'll see that a few of them (VW comes to mind) already have compound setups in production. Superchargers for compounds are generally easier to install on V-engines that inlines (supercharger rests nicely in the valley). Sequential turbochargers would be easier to engineer and install on a inline Miata engine and would provide most of the benefits of a compound setup.