Boosting the Mirage

[Loren]

Yes, you read that right. Justification follows...

The thought process of late has gone like this:

• I'd kinda like to supercharge the Mirage. But, it's a lot of work, and will it really be worth it? Maybe I should poke around and shop for another car, or at least see what's out there.
• The easy button answer for an undisputable "fast" car that meets my requirement of "lightness" is the new Miata. And it almost doesn't make sense to NOT buy the Club package with the LSD. (I'd consider it if the Sport package cars were cheap enough... but, they aren't) Best price on a 2016 Club is over $16k. Honestly, that's more than I want to spend. I could. I just don't want to. Y'all know me, I also have this thing for "driving slow cars fast", and the ND Miata just plain isn't "slow". Would it be fun? Sure. Would it be "me"... I'm not so sure.
• So, what else is out there? Something that I can run in S5 and really have fun with for a while without having to mod it to death just to have a little fun? Consulted the SCCA class list... H Street... there are the "hot button" cars, like the Fiesta ST and MINI Cooper S. Meh. I'm not trying to win a National Championship. What else is there? Something that's reliable enough to buy used with confidence, economical enough to satisfy my frugal side, but fun enough to compete in S5?
• Unfortunately, all of the lightweight S5 cars are either quite old, or silly top-heavy things like the Abarth 500. I'm tired of top-heavy tippy things. I want something stable. And, while I don't mind "slow", it doesn't need to be 78 horsepower slow! I looked around a lot. Looking at car specs, reading reviews, etc.
• Besides the obvious "Miata is always the answer", which doesn't fit in S5... I came up with three options that I rather liked. Cars that are either attractive, or at least interesting. Not too big. Perhaps a little heavier than I'd like, but powerful enough to still be fun. Good wheel and tire package (so that I can run 215 or 225 tires in S5... heh), and reasonable suspension.
• Dodge Dart GT - Has the same engine that's in the Abarth 500 and the Fiata. Not bad at all. Has a suspension upgrade that's firm enough that all the car reviewers comment on how firm it is... that might be a good thing. I've always liked the styling of this car. Upside: It's a Dodge, so it's depreciating rapidly. Downside: It's a Dodge with Fiat DNA... uh... this would be almost as dumb as buying the Mirage. But, admit it... you didn't even know there WAS a "Dart GT", did you?
• Hyundai Veloster R-Spec - This is essentially a de-optioned Veloster Turbo. And I'll admit that the ONE time I drove a Veloster Turbo when they first came out, I *hated* it. So, some test driving would definitely be required. But, it's fairly light (2800ish), very small (only about 8" longer than the Mirage), has funky fun styling, plenty of power, etc. And Hyundai reliability these days is pretty phenomenal.
• Hyundai Elantra Sport - This car is the winner. The only two things I don't like about it are that it's fairly long by my standards (18" longer than the Mirage), and fairly heavy by my standards (3100 pounds). It has everything the Veloster has, PLUS a much more refined independent rear suspension rather than the ox cart beam axle that's on every other FWD car. I've spent some time in a rental Elantra SE and really liked it. Add power, better suspension and tires and a manual trans? Hell, yeah! Sleeper autocross car.
• THE FINAL THOUGHT... each of those cars is likely to be in the $14-18k range. I'm just. not. ready. The payment would be something like $350/mo, and the insurance wouldn't be any more than the Mirage. But... it's $200 more than I'm paying now. Sooooo... maybe I can delay that for a while longer by adding some cheap power to the Mirage? That $200 over the course of a year adds up to $2400. I can very likely have a load of fun with the Mirage for the next year and a half or so for about half that. And after that... all of these other cars I've been looking at will have depreciated even further.
• THE KICKER... I drove the Mirage to St. Pete Sunday afternoon. It was cold. Well, colder than typical. Maybe 55 degrees? I could FEEL the difference in power from just that, and it felt nice. That couldn't be a difference of more than 2 hp. A little bit of boost could really make a difference.

Sooooo... I'm gonna do it.

The only hold up right now is that I need to take some measurements, and the car's not here. If the AMR500 roots supercharger that I have in mind will fit easily enough, it should be a fairly easy project. And there's an outfit in Asia that has a kit to fit a Rotrex centrifugal supercharger to the car... so, if the one fits, the AMR500 should fit. Oh, and the AMR500 can be had for under $300 shipped.

The Plan:

• Do the simplest installation possible.
• Supercharger bracket, tensioner pulley if requried, and intake piping.
• Boost Gauge and AFR Gauge.
• Restrictor plate on the SC inlet side to limit boost to no more than 3 psi. (this SC should be good for 4-5 psi)
• No electronics or fuel mods.

General wisdom says that each psi of supercharger boost is worth about 5% more power. So, 3 psi would be something close to 15%. I'm at about 85 hp now, so that puts me at around 96 hp. I think the stock fuel system can cope with that, and 3 psi shouldn't generate a great deal of heat or require any timing retard.

96 hp in a 1900 pound car. Still not even remotely "fast", but I think it will make the car a lot more fun. Then I can run the 2020 season struggling for mid-pack in M2.

For reference, the Rotrex supercharger installation looks like this. Note that they're using a supercharger that's capable of 6-8 psi or more, thus the recirculating BOV. And their kit includes larger injectors and fuel managment... and amazingly, no intercooler. They have it tuned to give a clean 30 hp increase. From 60 to 90 hp at the wheels. (probably around 110 at the crank) Full details on their kit if you're interested.

Anyhow... I like their layout, and will likely try to emulate it. But, I'm going for 3 psi. If I feel the need to go beyond that, then I'll have to consider how to add more fuel and all that. But, at this time... the plan is to just do this. Have fun with it for a while, and move on.

[Loren]

Here's the supercharger I'll be using:

https://bahnbrenner.com/vw_audi/product ... percharger



Budget:
$300 - AMR500
$50 - Materials for Brackets and restrictor plate
$100 - Idler Pulley and Belt
$200 - Intake pipe and couplers
$200 - Wideband and AFR gauge
$50 - Boost Gauge

Total: $900ish?

I've spent about the same for 5% increase in power from the header, exhaust and ECU tuner. $900 for 15% doesn't seem like a bad deal.

[Tim_M]

Another fun project!

3 psi seems hardly worth it? Still have the parasitic drive loss to overcome. I'd be surprised the OEM fuel system will tolerate it.

May put the car on a dyno before commencing and then post mod to provide good data and solid AFR curves - modifying engines pretty much require it. Then again, small, Japanese engines seem to be quite durable.

I enjoy the threads.

[Loren]

Parasitic loss is considered in the 5% per PSI figure. (exhaust driven turbochargers yield more like 7% per PSI)

"Worth it" is very subjective. Is 15% more power worth $900? I know a lot of people who have spent a lot more for less.

I'm not going to add to my expense with dyno time. That's a quick way to turn $900 into $2000. If I wanted to spend that kind of money, I'd be going a different route from the start.

I think almost all modern cars are designed with 20-25% of headroom in the fuel system. But, that's why I'm fitting an AFR gauge. If I'm not happy with the AFR's, I'll do something about it. It wouldn't be a stretch to fit a Microsquirt on the Mirage, just like I did with the truck. Only set it up in a Fuel Only mode. Leave the stock ECU controlling ignition and VVT and everything else, just control the injectors with the Microsquirt. Could do that for another $400 or so. But, that's not the goal. The goal is just simple and cheap. Make the car "a little less slow".

Really, $400 for the ECU plus a set of larger injectors is all I'd need to be able to double the boost pressure and get 30% or more. And maybe $100 for an intercooler. But, how far down the rabbit hole do I go? I'm not saying I won't go there... but, I don't plan to. Going that far is just begging for things to break. Transmissions, axles, clutches, etc.

[mymomswagon]

sounds like you've committed but I would add one car to the list (for future reference of course [emoji16]).

2015 Launch Edition Golf. Two door, 5 speed manual, supposedly weighs 2900, 170 crank horsepower, decent torque. IRS. Good aftermarket part / boost / engine analysis support. Guys show dynos in mid 2s with tunes and e30. Low 300s with turbo upgrade and intercooler upgrade. Pretty much everything for the GTI and Golf R can be made to fit. Only issue I've heard is clutches wear out fast on modded engines and some upgrade them to push the power envelope.

[Jamie]

Dodge Dart GT - Has the same engine that's in the Abarth 500 and the Fiata. Not bad at all. Has a suspension upgrade that's firm enough that all the car reviewers comment on how firm it is... that might be a good thing. I've always liked the styling of this car. Upside: It's a Dodge, so it's depreciating rapidly. Downside: It's a Dodge with Fiat DNA... uh... this would be almost as dumb as buying the Mirage. But, admit it... you didn't even know there WAS a "Dart GT", did you?

Actually, I test drove one of these at the Tampa Auto Show when they first came out. Drove reasonably well, but the lag on the small turbo was puzzling, and just sitting in it I could feel parts ready to fall off. I'd expect used ones to be cheap...and short-lived.

At some point, you'll have to look at the steering rack on the Mirage -- the last time I drove it, the thing that impressed me was how slow the steering was in comparison to the forward propulsion. And yes, I was moving my hands fast....

[CaptainSquirts]

Hey, I might he in M2 also for the 2020 season since evos are now DS class. We can fight for that mid pack together! Imagine the looks you'll get when people hear the super charger wine .

[mymomswagon]

Since when does Loren shoot for mid-pack?

[CaptainSquirts]

Since when does Loren shoot for mid-pack?

Have you seen who's running in M2?

[mymomswagon]

actually I think he would bump to M3 under current rules? If so that would explain it.

edit: then....245 40r15 rivals on an 1800lb car ... yeah baby!

[Native]

It's an M3 car that's "voluntarily" bumped down to M4.
"Cars in M3 may “bump down” to M4 if they have a tire size no wider than 205, and have no limited slip differential other than a factory Viscous type."
So the bump up is from 3-2.

[Loren]

Boosting an M4 car is a weird thing. We were in the same boat with the Festiva. The way the rules are written, our base class is actually M3. You're allowed to "bump down" from M3 to M4 if you meet the criteria. But, if you bump up... you're bumping up from M3 to M2.

I'm all about triumphing over physics with creativity, but it would take a LOT more than I'm willing to throw at it to be competitive in M2!

VW... I've got a mental block against VW. I used to be a fan, but I know way too many people who have had the dreaded VW electrical gremlins.

But, now my schedule is such that I won't see the Mirage until Saturday afternoon. Someday, I'll get to measuring the available space! I did find a belt routing diagram last night. Could get by with adding single idler pulley between the alternator and SC and use the existing alternator belt adjuster. But, the alternator will be under the SC... that might be awkward. Need to visualize it, it still might work.

[mymomswagon]

Sorry my mistake on the classing, just read your comments and the rules. Thanks for the explanation.

...but to save face for my foot and mouth, I predict that once you get out of LSD / 205 jail, this will not be your last mod [emoji16].

[Tim_M]

Chassis Dyno: $80 will get you three runs at WOT with AFR's. Do a baseline and then do it again after your mods. This will confirm the HP increase and verify the motor won't blow up on the autocross course. Seems like solid investment. Others on this board might support this.

[twistedwankel]

I remember reading quite a bit about electric superchargers in conjunction with turbos a few yrs ago to avoid lag. With a 1.2L engine I would think one of those would be a really easy addition for 3psi with an On/off switch and no parasitic engine losses BUT you'd have to put a bigger battery back in the car to run it for 60 seconds at a time. Sound like Mike's car yet? That would have to be a lot cheaper than a mechanical supercharger? Could be put on a rheostat to increase rpm with engine speed? Or just max boost at idle. Actually that sounds alot like Mad Maxx now:)

I was always able to run 50% more boost +5psi with stock fuel pump and injectors above 60*F in my old turbo cars. Below 60F the fuel cutoff would shut it down. They ran a lot richer back then? Maybe built with more excess capacity to keep rich and cool?

[twistedwankel]

Chassis Dyno: $80 will get you three runs at WOT with AFR's. Do a baseline and then do it again after your mods. This will confirm the HP increase and verify the motor won't blow up on the autocross course. Seems like solid investment. Others on this board might support this.

This is an awesome idea to see where one's car is from new!! Thanks Tim. Club needs a Dyno day:) Bet a lot of people will get a big shock how bad their car is performing. Of course the drag strip is only $20 every Thursday for some runs. Probably harder on the car than a dyno and less accurate due to tires/launch/wind.

[Tim_M]

Doug: funny you mention that as I just fought Chevrolet on my brand new 1LE. A dyno was the only way to convince corporate GM that my car was a dud - wrong program was loaded which took my 405 WHP down to ~266 WHP. Lots of drama, but without the factual data, I'd have no case. My drag strip times backed up the issue, but MPH is really the only good indicator with still a few variables.

See thread:https://www.camaro6.com/forums/showthread.php?t=542089

[twistedwankel]

Wow what a story. Thanks for all the info. Happy days in Germany.

[aw614]

You know I wonder if any of my filipino friends can get that kit with how frequently they travel back and forth between the US and ph. With weather that is even more humid and hot as Florida, Im shocked the kit doesn't come with an intercooler...

But I do like the supercharger idea over a small turbo.

VW... I've got a mental block against VW. I used to be a fan, but I know way too many people who have had the dreaded VW electrical gremlins.

Pre 92 VW fan, still doesn't explain why I bought the GTI in 2011, but the gremlins and problems are always on the back of my mind. I do not trust them making things reliable lol

[Loren]

Chassis Dyno: $80 will get you three runs at WOT with AFR's. Do a baseline and then do it again after your mods. This will confirm the HP increase and verify the motor won't blow up on the autocross course. Seems like solid investment. Others on this board might support this.

Monitoring boost and AFR with gauges will give me the data that I need to be sure that the engine is safe. The only thing dyno runs would add to that is the "how much power did I gain". I really don't need that number.

I'm also plenty interested in what the engine is doing in conditions OTHER than WOT. A data log or a video camera trained on the gauges as I'm driving around would be a lot more useful to me than dyno time.

There's more than one way to skin a cat. If you're tuning for max power at WOT, dyno runs are great. I'm not doing that. I just want "some" power, and to be sure my AFR's aren't too lean.