Turbo on a 95 L67

[irocjoecool]

I have a 95 Riviera L67 in my 87 Fiero. Several people in the Fiero world have had amazing results from turbo Series 2 engines. I would like to ditch my s/c and run an NA intake. I would also be intercooling the system.
What are the power limitations of a Series 1? Fieros with turbo Series 2 engines are getting north of 450whp.

[willwren]

That's a very interesting question best answered by the differences between the motors.

The Series 1 has heavier internals and doesn't rev out as high in each gear. It's more of a torque motor. You won't gain the same net horsepower mod for mod, but will gain more torque than the Series 2 mod for mod. In a light car like a fiero, this could prove difficult to launch and drive.

If you go that route, I'd be looking at a larger turbo to spool later to save your tires. Remove the nosedrive and rotors, and machine a blockoff plate for that end of the blower to use as your housing, not an NA intake. The only NA intake system that will fit your block and heads is an L27, and it's far too restricted with a tiny little throttle body. Your current throttle plate is already larger than that of the Series 2 L67, making your M62 housing and stock TB more ideal for an intake.

Series 1 L67's are probably (in general) a bit stronger than the S2 L67 in terms of stoutness and durability. You're just not going to get 450hp if you copy the S2 car that achieved that same goal. Probably 400-425 mod-for-mod. You will have more torque though, peaking at a lower RPM and staying flatter across the curve than the same S2.

EDIT:

I just saw your profile. You'd be best served getting a better trans than that 4T60. You'll need something stouter. Why didn't you stick with the HD the L67 was originally bolted to? I'm assuming you changed your shift points and gear ratios?

[irocjoecool]

The 95 Rivi trans is a non-hd 4T60

[willwren]

Not true. If it came under the L67, it's actually a 2.97 ratio HD trans, by use of a 3.33 ratio differential which is quite a bit more beefy than the standard 4T60's diff, and larger diameter axles. While not 'tagged' or otherwise identified as an HD, it was in fact so. The axle ratio is the giveaway clue.

Non-supercharged got the 3.05 axle ratio just like the H-bodies on this Forum, and the L67 equipped 95 Rivieras got the 2.97 ratio, just like both the 93 and 95 L67's that I own (in H bodies).

If you didn't account for this, and you're using the Riv PCM in stock tune, your shift points are wrong for that 97 4T60E, which is very likely a 3.06 ratio.

[irocjoecool]

Ryan Glick did my tune and did account for the ratio change. The trans is from a 97 3x00 Grand Am. The Rivi trans was shot and the GA trans was free.

[Jrs3800]

Ok just to make a note here.... 95 was a freak year for a lot of different things in GM....

Do you still have that 95 Riv SC trans? 95 was an odd ball year, the 95 SC Bonnevilles got the 2.97 ratio trans using a 3.33 diff...

The 95 Riv if it had the original trans got the 2.93 overall ratio using a 3.29 HD Diff, but this diff is the only year to have a reverse fine pitch... It will only work in that trans and no other due to the ring gear... in 96 they changed the pitch again and then left it alone...lol...

If you do have that 95 Riv trans it should have the one off 3.29 HD Diff... This was the only car i know of to have this set up until 96 when the other Supercharged H and C bodies went to it...

[willwren]

Don, I'm finding conflicting info on that. I'm seeing 2.97 ratio for the 95 Riv.

In either case, the original Riv trans was stronger than any non-HD 60 would be, especially if your plans include a turbo and the 400hp range.

[Jrs3800]

I really need to find time to get better pics together... It seems what GM said they did and what they really did is not exactly correct...

The G body, NA 3800 used the 3.05 Diff, and the SC G body used the 3.29 diff for 1995( both of these being reverse fine pitch).. The 95 C and H body used the 3.33 diff for SC and 2.84 and or 3.06 for the NA( Regular pitch )...

1996 all of the SC C, H and G bodies all used the 3.29 Diff( fine pitch )


Its really screwed up how GM did all of this...

But here is the problem... There were regular pitch Diffs( 2.84, 3.06 and 3.33 ), then you had the Reverse fine pitch 1995 only 2.86, 3.05 and 3.29...

Then in 96 it was Regular fine pitch 2.86, 3.05 and 3.29... But the 96 fine pitch will not swap for a 95 reverse fine pitch or the other way around...

Now from what I can gather, the 2.84, 3.06 and 3.33 stayed a regular pitch and the last year for the regular pitch was 1997... 98+ is all fine pitch...

Only reason I have learned or had to learn this was due to the issues I was having finding the correct diff I was looking for.. GM really mixed it all up on this one...lol

The reason I was diving into his trans is that if he has this Riv Trans, he can also upgrade to the newer ring gear and run the 98+ 3.29 diff, and if it ever breaks he would have an easier time sourcing another... The 95 Riv trans was very one off..

[00Beast]

I'm trusting Don w/ this one, LOL.

[GonneVille]

Honestly, if I were building an L67 Fiero, Series 1 or Series 2, I'd drop the auto and put in a stick, either a Getrag 5spd, or the 6spd from the G6.

Fieros with big power are pretty twitchy in the corners, and a badly-timed shift from an auto could cause you serious grief. Unless you're only going to use this thing for commuting and drag-racing, manual is the way to go.

[01bonneSC]

Honestly, if I were building an L67 Fiero, Series 1 or Series 2, I'd drop the auto and put in a stick, either a Getrag 5spd, or the 6spd from the G6.

Fieros with big power are pretty twitchy in the corners, and a badly-timed shift from an auto could cause you serious grief. Unless you're only going to use this thing for commuting and drag-racing, manual is the way to go.

I say manual is the ONLY way to go in a lil fire chicken. Much more driver input available and lighter.

[ga93sle]

Not to mention just plain cooler...

[willwren]

In any case, the non-HD transmission is a bad formula for success if you're considering a Turbo. Regardless of FDR. You have the wrong transmission, plain and simple.

[irocjoecool]

In the Fiero world, 5 speeds are generally slower and pretty fragile in high hp Fieros.
First gear is basically useless in the Isuzu and Getrag 5 speeds with higher-torque engines,.