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Old 06-13-2005, 02:46 AM   #1
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Default turbocharging an L27

i am totally new to the Buick 3800 engine, and have a few questions about turbocharging the L27. basically i'd like to add 8-10psi with a FMIC. some questions....

- what is the compression ratio of the L27? i've heard some people say it'* 9.0:1 and others say it'* 8.5:1

- what would be the best way to block off the rear exhaust manifold dump? simply block it off or? would it be possible to use exhaust manifolds from a RWD 3.8L engine on an L27?

- how much boost would the stock MAF sensor handle? how would i add fuel and timing? would it be better to go with an aftermarket speed density standalone system?

- how would the stock L27 cam react to boost? too much overlap? is the L67 camshaft any different?

any ideas, suggestions, discussion much appreciated. please no replies like "just drop an L67 in there" i might just end up doing that, but i'd like to know what'* going to be involved in turbocharging the L27 first.
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Old 06-13-2005, 02:51 AM   #2
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Default Re: turbocharging an L27

Quote:
Originally Posted by malibuolds
- what is the compression ratio of the L27? i've heard some people say it'* 9.0:1 and others say it'* 8.5:1
8.5:1
{quote]
- what would be the best way to block off the rear exhaust manifold dump? simply block it off or? would it be possible to use exhaust manifolds from a RWD 3.8L engine on an L27? [/quote]
You'll need to modify your manifolds, RWD ones will not work. You could run the turbo off the crossover, MAYBE the downpipe, but that'll be close to a lot.

Quote:
- how much boost would the stock MAF sensor handle? how would i add fuel and timing? would it be better to go with an aftermarket speed density standalone system?
The MAF is the same as the L67 one, and members here have seen 12psi easy in 1993 throttle bodies (atleast 1993 parts are the same, 94 L67 might be different) Aftermarket might cost A LOT more then good tuning.

[quote]
- how would the stock L27 cam react to boost? too much overlap? is the L67 camshaft any different?
[/quote
I dont' know if the cam profiles are different, a stock cam should do ok with boost, it'* a VERY mild grind designed with reliability, and smoothness in mind

Quote:
any ideas, suggestions, discussion much appreciated. please no replies like "just drop an L67 in there" i might just end up doing that, but i'd like to know what'* going to be involved in turbocharging the L27 first.
The 3800 series I has a very weak upper end. A turbo is the best way to cure that. It'd be a great project, and i believe a member here is working on turbo'ing a 91 (very simliar) so keep your eyes peeled.
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Old 06-13-2005, 03:04 AM   #3
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i was planning on getting a custom crossover pipe made, probably with a flange for a T04E turbine. i still don't know what to do about the rear exhaust manifold though. i'd imagine a set of custom headers would be serious money but it sounds like the only option so far. sucks i can't just use a set of RWD 3.8L manifolds :(

as far as extra fueling goes....would an FMU and bigger injectors do the job or would i need a custom burnt EPROM (memcal)? i wouldn't even know where to begin as far as editing the EPROM code goes....does anyone out there sell reprogrammed memcals? i would really like to avoid an aftermarket standalone system if possible.

thanks
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Old 06-13-2005, 11:28 AM   #4
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GM tuners for you, you will need scantool data, but talk to them and see if they can help you out. you maybe can use */C data

oh and BTW there is gonna be alot of info for turboing a NA car real soon and you will be surprised
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Old 06-13-2005, 01:54 PM   #5
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a standalone FMU might be easier if you can tune it yourself. An M62 will build boost very different compared to a turbo, so you can't use their fuel tables.

A T03 or T03/04 hybrid might be better for you, the smaller they are the better they spool.

For the manifold you might just wanna chop the downpipe connection off of the rear manifold, and have it welded closed.
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Old 06-13-2005, 02:11 PM   #6
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Wow no one has said "Drop in a l67" even though people say dont say that it still pops up lol.
Who was turboing the series 1 on the forums?
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Old 06-13-2005, 02:54 PM   #7
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Before you even start you need to sit down and think what your goals are for this car and what kind of power you want. That is going to be the big X in this whole project.

As for fueling just off the top of my head your going to need a fuel pump, bigger injectors, and a alt. rewire/fuel pump rewire for the bigger pump.

As for tuning I'd hit up DHP. . . . .they'll do custom tuning for crazy projects.

More then likly your going to have to throw a MAP sensor on the car since that is what is really used at WOT and the MAF for the inbetween stuff.

If you look at the cartuning kit you might be able to get some ideas off of that - headers wise.

Only problem I see is your trans - by putting a turbo on a 3800 and trying to throw down any kind of power your just asking for the trans to grenade - esp. with a bonne being a tank weight wise.
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Old 06-13-2005, 09:57 PM   #8
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It can certainly be done. I have a turbo on an LN3, and it has been running as a daily driver in the summer for two years. The chip has been a problem up until now and Ryan @ GMTuners has made me one but it hasn't been trialed yet. Exhaust piping is a fair amount of work and it is easiest if you have a spare engine hanging on a stand. There were no kits available six years ago when I started this, so there may be a bunch more available now. One thing to think about is there is less parasitic loss with a turbo, although the response is different than an */c, and 7 or 8 psi will give you approx. 50% more hp. Different strokes. The trans. is always a concern, but mine has 112k (20 k with the turbo), and so far so good. Full power starts are probably not a good idea, but it will work if discetion is used. Even the older GN'* didn't have boost sensing to the ECM, so that isn't critical, but it would likely make tuning easier if such a system were used.
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Old 06-14-2005, 07:31 PM   #9
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Quote:
Originally Posted by llBlazin_llLo
Before you even start you need to sit down and think what your goals are for this car and what kind of power you want. That is going to be the big X in this whole project.
i think my only goal is really just to have a dependable engine with 10psi. i know the transmission is going to be a different story altogether. however, more than likely i will run the 4T60-E into the ground while i have another built. i would like to reach 250whp, and maybe 280wtq. weather that is possible with 10psi, large FMIC and good tuning i really don't know....yet.

i won't be starting this project for quite awhile. i'm sure alot of planning and research is going to be involved; i'm just starting. i may go with a T3/T4 hybrid instead of a full T4, i still don't know which injectors i would use, etc etc.

my first turbo project involved my GTS, which was already turbocharged from the factory. that car is basically stock besides larger exhaust, and supporting mods for more boost, such as Walbro 255 fuel pump, grainger valve MBC set to 14psi (just under factory fuel cut), 1gDSM BOV, redone all vacuum lines with McMaster-Carr manifold distribution block, new motor and trans mounts....LOTS of small stuff, even though the only 'go-fast' mods are full 2.5" mandrel bent exhaust and boost controller turned up about 2psi over stock.

my 2nd turbo project was my Cutlass. i simply turbocharged the existing 3.1 MPFI engine with parts from the Turbo Grand Prix, along with a modified EPROM for use with the 5-speed ( i swapped in the Getrag 282 5-speed 100% myself), rebuilt crossover pipe with new SS flex bellows, new Melling HV oil pump, etc. it also uses a grainger valve MBC instead of the ECM controlled wastegate solenoid, just like my GTS, as well as a Walbro fuel pump. otherwise it is a stock TGP engine.

i think i'm ready for something more challenging now. while my other two turbocharged cars are speed-density, the L27 is of course MAF which is totally new to me. i also can't just use a factory turbo rear exhaust manifold and turbo crossover pipe like i did with the TGP engine in my Cutlass, and there is no turbo-version of an L27 memcal, so these things are going to have to be totally custom. right now, i see the rear exhaust manifold, crossover pipe, and modified EPROM/memcal as the hardest part of this whole project. i can't fabricate the rear exhaust manifold/* or crossover pipe, not to mention i can't weld. i also can't just go and edit the EPROM myself, as i don't even have a PC, PP2, or even chip editing software like GMPCM yet. i don't even have a scan tool for the Bonneville yet. everyone has to start somewhere though
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