Most efficient route to reach 350HP in an e30?

[Blackdave458]

Cheapest and easiest route is turbo the m20. They are dead reliable, cheap, and easy to work on. I've done countless 300+whp m20's and it only takes 1bar on a 60-ish mm turbo.

Would you recommend 2.5 L 325IS m20's for this? The whole timing belt failing to catastrophic engine failure situation which i've read about scares me from turbo'ing an m20 but please share any experience with me on that if you can, im all ears!

[Blackdave458]

Cheapest, turbo M20, fast but definitely not a smooth power delivery.

More reliable still cheaper just not as much as the M20 is an S50/2 Turbo, power delivery is better but still laggy.

More expensive and complex but the most natural feel go S54 with Rodbearings and Vanos rebuild and a few other mods you will touch 350 but it will be very reliable linear power, just less TQ but the E30 is so light you dont notice.

S54's seem VERY nice. Although checking the price of them is insane.. around 7/8 grand. How would you compare the S54 to an m62 as far as linear power? The m62's are soooo much cheaper but Id love to hear your insight on that

[Blackdave458]

In the OP it was stated "my 325iS", made a strong guess it's a b25. ;)

Yes, its a m20b25

[Blackdave458]

did you s54 guys miss the without spending too much note? metal snail on current engine for sure

Yeah, my e30 is too slow for my desired heart rate lol.

[Blackdave458]

Cheap, fast, reliable. Pick two.

S54 will cost more, but IMO is your best bet. Once set up correctly, it will be reliable, provide linear power, and won't require so much tinkering.

My experience with turbos = constant fiddling around with it to get it right.

Thank you

[Blackdave458]

Turbo M20 is definitely cheapest/easiest. Typical costs just off the top of my head...
.
Turbo $700+
Header $500+ (honestly just shell out and get a really nice thick one made by a pro fabricator, even the decent production ones crack or come with warped flanges)
Injectors $300+
Megasquirt $500+
Wideband gauge/controller/sensor $200+
Fuel pump $150+ (for one that won't just crap out on you)
Wasted spark conversion $150+
Head studs $200+
Clutch $400+ (do NOT buy cheapo clutches)
Intercooler $100+
Piping/couplers $50+
BOV $50+
External wastegate $250+ (if you choose to go that route)
Oil pan modification and oil drain and feed line $150+ (unless you can TIG the aluminum yourself)
Motor mounts $dick (just buy hockey pucks and drill and cut them, the poly aftermarket mounts are a waste of money at $60+ for a chunk of poly with a hole straight through it, a stud and a washer)
Exhaust $???? I've never paid to have one made, I just booger it together with parts from columbia river mandrel bends with my $150 welder. Honestly it's worth just buying a cheap harbor freight welder to do this because the labor will cost twice the cheap welder
Tuning $300+ (if you teach yourself, be careful. I've cleaned up messes after quite a few people who underestimated the task)
Incidentals $good luck
Labor $toomuch

You aren't getting out of it for under that unless you have the stuff laying around or cut corners. Ebay turbos don't last, used turbos always wind up needing a rebuild eventually which is $200+ done right with a balance and holsets aren't $150 like they were when I got into cheap turbo cars, walbro fuel pumps are a stupid thing to buy at this point because knockoffs are everywhere and walbro does not warranty the genuine product... Double the cost above if you can't do the work yourself and fabricate.

Thank you for that... Seriously. Well it gives me a goal to save up for. I was hoping to spend around 8-12k or less but. Seems like its within that range on anything higher than a turbo m20.

[MayaWilson]

Cheapest, turbo M20, fast but definitely not a smooth power delivery.

More reliable still cheaper just not as much as the M20 is an S50/2 Turbo, power delivery is better but still laggy.

[Andrew325is]

C'mon, don't be cheap. Do it right. Build a 350hp NA S14.

[digger]

E30 with m20 reaching 140 lol. Sent from my SM-G973U using Tapatalk

190rwhp = job done

[ForcedFirebird]

E30 with m20 reaching 140 lol. Sent from my SM-G973U using Tapatalk

I have hit terminal velocity many times in e30's at Daytona, twice per lap - probably for thousands of laps over the years. With Spec e30 trim (~155-160whp) they are aero limited to about 125mph, can see a tad over 130mph with bump drafting (I saw 134mph once). Even with a draft, you won't hit the rev limiter in 5th, it will float about 6-6200rpm.

With 180whp/180wtq we hit the rev limiter in 5th without a draft, 4.10, 7100 limiter, 225/45 15. Don't have GPS in this car, but that should be over 140 according to gear ratio vs speed. After about 130 the car is quite "floaty" in stock form. We don't have any points left to put aero on our cars.

[Staszek]

I have hit terminal velocity many times in e30's at Daytona, twice per lap - probably for thousands of laps over the years. With Spec e30 trim (~155-160whp) they are aero limited to about 125mph, can see a tad over 130mph with bump drafting (I saw 134mph once). Even with a draft, you won't hit the rev limiter in 5th, it will float about 6-6200rpm.

With 180whp/180wtq we hit the rev limiter in 5th without a draft, 4.10, 7100 limiter, 225/45 15. Don't have GPS in this car, but that should be over 140 according to gear ratio vs speed. After about 130 the car is quite "floaty" in stock form. We don't have any points left to put aero on our cars.

I think the E30 is quite scary over 130, yours was probably set up better, but damn mine felt really floaty when I hit 130. You really forget how smooth modern cars are at those speeds until you drive one of the older cars. And the E30 is kinda brick.


Someone mentioned the M62, its actually a really good cheap choice, tons of power, its heavy though so handling will suffer a bit.

[ForcedFirebird]

Would you recommend 2.5 L 325IS m20's for this? The whole timing belt failing to catastrophic engine failure situation which i've read about scares me from turbo'ing an m20 but please share any experience with me on that if you can, im all ears!

Putting a turbo doesn't have anything to do with the timing belt. As long as you change it with normal intervals, they will last all the same. I have built and tuned many customer m20 turbo's over the years, several of them daily drivers with tens of thousands of miles on them.

[R3Z3N]

I have hit terminal velocity many times in e30's at Daytona, twice per lap - probably for thousands of laps over the years. With Spec e30 trim (~155-160whp) they are aero limited to about 125mph, can see a tad over 130mph with bump drafting (I saw 134mph once). Even with a draft, you won't hit the rev limiter in 5th, it will float about 6-6200rpm.

With 180whp/180wtq we hit the rev limiter in 5th without a draft, 4.10, 7100 limiter, 225/45 15. Don't have GPS in this car, but that should be over 140 according to gear ratio vs speed. After about 130 the car is quite "floaty" in stock form. We don't have any points left to put aero on our cars.

Yup, I was doing 140 in turns 1-2 according to my speedo (which as I stated is off quite a bit) when it was s52 swapped at Fontana. As you state, its quite floaty. I actually spun as someone came out of the pits illegally before the white pit line ended and I had to lift. I didn't even touch the brakes...

With the S54, I was able to get a little higher, but I won't say....

[ForcedFirebird]

With the S54, I was able to get a little higher, but I won't say....

Why not? Closed course. Can't trust the stock speedo, mine would indicate 140+ drafting when I know right well that's not 4.10 and 5th @ 6200 (GPS said 130-134). With the 180whp motor the speedo goes right around past all the tick marks.

The 2.8 ITB car we built a few years ago buries the speedo - 7400 limiter and 4.10, also 225/45 bangs the limiter, it makes 212whp.

I hope you mean NASCAR 1 & 2, the Rolex T1 at Daytona is a ~170° tight left. o.0

[Andrew325is]

On a more serious note, why is 350hp the magic number? There is more to consider than just the power figure. You might want to explain to us how the car will be used. For example, for high speed spirited driving on the track, interstate, and rural roads S54 is a great option, but driving in the city feels like you're holding back a wild horse that can't breathe. For city driving and curvy roads you'll have more fun with a lightweight 4 cylinder like an M42. There are good reasons why BMW raced E30s with 4 bangers... You could slap a supercharger on one, but of course it'll cost serious coin to get it to 350hp. Also, the S54 doesn't need the dual pickup pump and pan unless it'll be used for very aggressive driving. Its Euro S50b30 sibling didn't have that (except for the limited GT).