Unlocking power from a 3.2 when moving to 3.7-3.8 -...

[LT86]

Hi everyone,

I own a european 1986 carrera 3.2 which I use for 90% spirited driving on the road and about 10% tracktime on racetracks around Belgium. After enjoying it for a few years I decided to rebuild the 3.2 to a 3.7-3.8-ish (or bigger) motor and would like to pick your brains to get some advice and experience on a proper build.

Current setup: 3.2l, 915 transmission with LSD. The engine is in good condition and has small mods: SCART exhaust, FVD MAF kit with chip and light flywheel. Rest is stock.

Goal: To build a very responsive, high(er) power engine. I'm not looking for only top-end power. Rather strong mid-range which continues in a good top-end pull. For responsiveness I would like to shed good internal weight with lighter parts. Not sure what power is possible (300-340?)

Questions for the setup:
- Crankshaft: Updating to a 80.4mm. I have read in various places to use a GT3RS 4.0 crankshaft but not sure if this is the way to go as it seems to have different piston pens diameter which I don't find how to link with conrod/piston set.
A german shop sells an 80.4mm one which I assume is the way to go.

Do you recommend to install a harmonic damper to cope with vibrations as well?

Conrods: Mittelmotor recommends 3l modified conrods. I've heard good things about CP-carillo conrods but any recommendations are welcome.

Piston and cilinders: I assume to use MAHLE (?) 3.2 to 3.4 kit but what I'm lost on is that these have 23mm piston pens for a 3.2 but the 3l conrods would have 22mm pens. So what can I do here? Also, the 3.2 to 3.5 kit would work (same question though) but I'm not sure if I need to start modifying the bottom of the engine block for clearance than.

Camshafts: What do you recommend? 964 or 964 cup cams maybe?

Injectors: I've read here stock injectors will run out of duty cycle and saw 993 or 944 (green) injectors as recommended for these kind of setups. Thoughts?

Heads: will keep my 3.2 2-valve setup but can put but bigger valves in them and have the heads redone. Also not really planning to go overboard and convert to twin plug ignition for the following reason:

Intake: Due to homologation in Belgium I need to keep the engine looking more or less stock so I will keep the MAF converted intake as well as the SCART exhaust. A specialist told me potentially the motronic could be al limiting factor for this setup but with 3.2 valves being nearly the same as 3.6 I take it it would be caused by the ports? As for the motronic. I could just up fuel pressure and change injectors to cope with this, no?

Engine management: once the full setup has been completed I will have a chip made for the setup.

Please excuse me for the long read but I'm trying to be complete and hope to get some good feedback and possibly tips from people who've done it before.

Thanks!!

[JoeMag]

Regarding rods...
- If you're going to have custom rods made, you do not need to worry about wrist pin dia or rod bearing dia, just have them made to what you need.
- Need to think about length. Do the calc to see what you need; center line of case to surface where cylinder mounts is 115mm.
- With carillo rods you may need to clearance oil pump.

Not sure how much power you can make with the 3.2 intake. ...maybe other's can chime in.

[Bill Verburg]

Originally Posted by LT86

Hi everyone,

I own a european 1986 carrera 3.2 which I use for 90% spirited driving on the road and about 10% tracktime on racetracks around Belgium. After enjoying it for a few years I decided to rebuild the 3.2 to a 3.7-3.8-ish (or bigger) motor and would like to pick your brains to get some advice and experience on a proper build.

Current setup: 3.2l, 915 transmission with LSD. The engine is in good condition and has small mods: SCART exhaust, FVD MAF kit with chip and light flywheel. Rest is stock.

Goal: To build a very responsive, high(er) power engine. I'm not looking for only top-end power. Rather strong mid-range which continues in a good top-end pull. For responsiveness I would like to shed good internal weight with lighter parts. Not sure what power is possible (300-340?)

Questions for the setup:
- Crankshaft: Updating to a 80.4mm. I have read in various places to use a GT3RS 4.0 crankshaft but not sure if this is the way to go as it seems to have different piston pens diameter which I don't find how to link with conrod/piston set.
A german shop sells an 80.4mm one which I assume is the way to go.

Do you recommend to install a harmonic damper to cope with vibrations as well?

Conrods: Mittelmotor recommends 3l modified conrods. I've heard good things about CP-carillo conrods but any recommendations are welcome.

Piston and cilinders: I assume to use MAHLE (?) 3.2 to 3.4 kit but what I'm lost on is that these have 23mm piston pens for a 3.2 but the 3l conrods would have 22mm pens. So what can I do here? Also, the 3.2 to 3.5 kit would work (same question though) but I'm not sure if I need to start modifying the bottom of the engine block for clearance than.

Camshafts: What do you recommend? 964 or 964 cup cams maybe?

Injectors: I've read here stock injectors will run out of duty cycle and saw 993 or 944 (green) injectors as recommended for these kind of setups. Thoughts?

Heads: will keep my 3.2 2-valve setup but can put but bigger valves in them and have the heads redone. Also not really planning to go overboard and convert to twin plug ignition for the following reason:

Intake: Due to homologation in Belgium I need to keep the engine looking more or less stock so I will keep the MAF converted intake as well as the SCART exhaust. A specialist told me potentially the motronic could be al limiting factor for this setup but with 3.2 valves being nearly the same as 3.6 I take it it would be caused by the ports? As for the motronic. I could just up fuel pressure and change injectors to cope with this, no?

Engine management: once the full setup has been completed I will have a chip made for the setup.

Please excuse me for the long read but I'm trying to be complete and hope to get some good feedback and possibly tips from people who've done it before.

Thanks!!

the 3.2 block is the limiting factor on piston diameter
the 3.0 thru 3.2 blocks have 86mm stud spacing, limiting the pistons to 100mm w/ very thin and fragile spigot walls. 100mm pistons on a 76.4mm crank yields 3506cc

100mm on a 80.4 is 3789cc

if you must use the 3.2 blokc stay w/ 98mm pistons max w/ a dome to match the intake/management profiles

a harmonic balancer is recommend but likely unavailable unless you use a GT3 crank

the next weak link will be the trans a late 915 is pretty comfortable w/ a stockish 3.6 but gets much less so w/ a slightly breathed on 3.8, the issue is more in the lower gears but not limited to them

jmo here but

put a 3.6 993 engine in there w/ ITTBs and Cup or ss cams. w/ good headers and freeflow muffler, if money is no object add Extreme cylinder heads

[GG Allin]

Originally Posted by Bill Verburg

.............. 100mm pistons on a 76.4mm crank yields 3506cc

.........

100 x 76.4 is 3.6 on the nose. I run this configuration in a 3.2 case.

Did you mean 100 x 74.4?

[LT86]

Thanks, Joe!

In the meantime I've received word from the company where m buying the parts. According to them the motronic will do around 300 max with this setup, 320 if I also work the heads and install bigger valves.

I'll go with the gt3rs 4.0 crank with modified pulley, lightened rods and have the pistons made to fit. Cilinders I can have mine bored (will go 98mm) and re-done or opt for the MAHLE 3.2-3.4 kit.

Still wondering which injectors to use.

Bill, yes, makes sense! This would be the easy route but due to homologation law I need to keep the engine looking stock-ish. If a different engine would be spotted during MOT the car would receive a red card and be no longer allowed on the road. Also the reason why I unfortunately can't go ITB.

[stanglife]

You need a beer buddy at the inspection station

[JoeMag]

Couldn't figure out how to get link of an old thread regarding 993 injector, so here's cut...

[MoreGAS]

Man after my own heart! A roaring engine that really makes power is the heart and soul of these sports cars.
More displacement is the solid and best way to make a road car more powerful and enjoyable, but remember to really make power you are going to need more air and more camshaft(overlap especially) to get the air in the cylinders at higher RPMs. This will not pass emissions or an ear inspection if you are tested there, are you? Are you allowed headers as the stock exhaust is not great for making power, as there are not tuned pulses which really wakes up the Tqe in the middle and keeps it better top end.
You'll need a custom piston for certain w that stroke crank and different rods as well as a stock 3.0 rod (which is crazy heavy but stout) modified is going to have clearance issues with rods hitting the pump because of the shape of the bottom of the rods, vs say a Gt3 rod or Carrillo(we make a custom Rod via Carrillo for our application) Pauter etc.. where the bolts come in from the other side(no square lower corners) . As a matter of fact a 4.0 L Gt3 has a different oil pump to clear the rods and the std Gt3 pump doesn't clear. I believe also the 4.0 rod is shorter than std Gt3 . You would be wise to atleast put in a 964 pump or better a Gt3 pump.

We have built a few custom 3.55 L street hotrod engines 78.6x 98mm w great tqe little over 300 HP old school MFI and ITBs, and the tqe is what really mkae sit impressive to drive. Also a 3.75L (race engine) in a 3.2 case what Porsche calls a 3.8 using a custom crank and 100 MM bore that really kicked ass, over 360hp to the wheels 280 ish Tqe from memory w Motec and ITBs, great headers, great heads... But, your intake will really hold you back as it is going to make peak power at 6200 rpm almost no matter what you do with a cam, so don't over do the camshaft, also don't waste loads of money on the heads(as suggested w custom heads) just put largest valves that will fit stock seats if in good shape, great valve job, port tidy up, as again the intake plenums will hold back the top end. The stroke and displacement addition will help a bunch where you spend all your time on a streeter 3K-5500 RPM. We've tried that (really trick heads) as a preliminary step and the 3.2 intake did just that , also more cam did almost nothing vs a moderate cam well selected.
The integrity of the 100 cylinders is very close to the 98s as the extra 2 MM bore change happens in the spigot area bored in the case, also deck the case at this time while easy and set up. We have also at times made custom cylinders w press in ductile ron liners inside the alum finned portion to have better cylinder integrity and keep shape better under big forces and pressures, we've done this at 102 mm also on 3.6 platforms. SO if 100 MM is your goal it can be done and even bored in 100s for a streeter (avail from LN engineering-real pricey though) would perform well. Even all aluminum(nikasil coated) at the moderate compression ratio you'd be at for a single plug streeter would be fine. We have even modified 3.6 100 mm barrels w a bunch of machining to fit 3.2 stud spacing and ran them for years , cal it a cheap charlie option I did on one of my own cars,( not sure I'd sell to a customer). We have also run this cheap charlie arrangement on a 3.3 tbo and it lasted a long while making a 3.5 L . Avoid these crazy bore goals of 101 mm and up , or 103+ for 964 cases, for this application though, and prioritize ring seal and bore shape over bigger is better; there is a limit.
You cannot just swap injectors but will need properly sized injectors and a custom chip tuned to match the new power levels and fuel demand to match the airflow changes. It will be a system, totally new.
So you will need many bits, several custom in nature: Rods, crank, pistons, cams, machining galore, build expertise double, an oil pump, and many other upgraded bits-head studs, bearings, Valves, springs and retainers on and on....It is easy to see how this quickly gets well beyond most folks' pocket book outdoing their car's total value.

Lastly, realize a MM inside an engine is a mile, and you are considering adding= 6 mm of stroke, 3-5 MM of bore change, inside a case it was never aimed to be inside of...so undertaking what you are considering is huge deal, so better make certain your builder has done this before- successfully.

You can tell by my rambling what I am passionate about here lol... and are welcome to PM me for specific questions to hone in on your plan if desired.

Good luck
Kevin
GAS Motorsport

[LT86]

Really getting good information, thanks all!

@joemag, I mentioned the 993 injectors because in another thread someone said they should work for this kind of setup, seems the one you posted speaks differently.
Do you, or Kevin (GAS) have any recommendation on what would work for injectors then? I will have the car put on the dyno to remap afterwards so just to know if I should change the fuel pressure regulator and which injectors would hold enough duty cycle.

The German shop I'm ordering from matched parts so I'm nearly done on deciding the setup. They will provide the crankshaft (80.4mm), the racing rods and will have pistons made to match the setup. I will provide old 3.2 cilinders which they will bore to 98mm and re-nikasil. So I guess it will be a 3.638cc engine. I also saw that LN engineering kit but I was wondering if the additional price was worth it.

Another option is to ask the shop if they can bore out to 100mm and fit custom pistons. This will give 3788cc to provide a bit more torque (so to focus on midrange not peak power)

However, still my biggest blind spot is how limiting the current intake will be (with the MAF kit mounted). Big thanks for the information on this one, Kevin. The shop also has a set of sport cams specifically for the K-jetronic/Motronic not to go overkill and keep the power in the range where the intake plenum still delivers.

Also, does it make sense to fit bigger valves if I don't rework the ports? (Don't know a shop qualified at the moment) and does it make sense to go for 100mm if I don't fit bigger valves. A lot of ifs, haha.

And lastly, yes! Luckily they don't give us a hard time on aftermarket exhausts (within reason) so I have a cat-delete and SCART exhaust on the car to give some more flow.
Happy with this setup so I'm keeping it.

Originally Posted by stanglife

You need a beer buddy at the inspection station

[MoreGAS]

Hello. There are many online injector calculators avail to help you select your injector size based on fuel type and engine criteria(normally aspirated) and HP goals. Look some up. I recall your 3.2 injectors are high resistance so you have saturated drivers in your ECU and will need to maintain the high resistance nature of your new injectors. For engine like these we use a more modern design Bosch injector w plastic body to avoid additional heat transfer and a 4 hole nozzle to help w atomization , stainless steel internals so suitable for numerous fuels. 30 lb per hr will be fine (maybe even a bit smaller one size down in Bosch line) and I would pass on any old Porsche injectors as with spark plugs they just rip folks off on Porsche pricing. Running higher fuel pressure can also assist in better atomization and you can fit a 3.6 964 fuel pressure regulator to run 4 BAR or 60 psi fuel pressure. We used to be able to buy adj. fuel press reg'rs for 3.2s that bolt right into stock arrangement but today we're having a hard time locating one. This will allow you to run smaller injectors, perhaps even 25 lb range .Smaller injectors generally have better response times but the new crop of modern injectors handle this latency so much better it is not as much of a concern today vs what you have and Porsche's next 964 injector etc. We can help supply what you need-modern, clip in to stock arrangement if you cannot find this w confidence. Oh yah, any injector we use or buy will be matched sets that are within 1% flow variance in sets(they test them and match) . Ebay and amazon are not where one should look for these...

You cannot bore 3.2 cylinders to 100 mm(there would be almost nothing left) , that is why I mentioned LN cylinders as you need larger OD on spigots and the case bored to 2 MMs larger to get the 100 ID dimension. Even then correct 100 cyl's get so thin in spigot bore wall thickness, roughly .090" I recall, as noted we go to the ductile iron type lining to keep integrity sometimes on higher Perf. applications. If you grab a 98 MM bore cylinder down low, and squeeze it between your fingers while checking w your bore gauge , your eyes will pop out when it closes up .002-.003" . How does it do with alot of temperature increase, and big side thrust forces with increased stroke(which is why longer rods help) and side loads(?), scary.

Rods- stock 3.0 rods are THE heaviest rods Porsche makes( and I have seen scary work lightening them up losing all their strength ) , and I don't think they will work with that crank. You need aftermarket of a different design as noted to clear the oil pump. Many Co's in Europe also make quality upgraded rods besides those I mentioned. If a stock rod is used upgrade to ARP bolts or Raceware no matter what(but they will not clear again).

Heads yes when one fits larger valves, you need to open up The seat ID to a proper proportion and focus on the bowl too. The restriction is in this area, not the valve necessarily or the 41.5 mm port. 3.2 heads flow as much as a 964 head stock. This work is for experienced folks who have used a flowbench and accumulated associated Dyno data on The real performance.

Bigger the better, no replacement for displacement. Especially w whimpy cams and poor exhaust.
Not sure what your exhaust system is but headers w tuned length pipes and good collectors, and a well designed muffler are paramount. You are having custom pistons made so make sure there is adequate valve reliefs to fit more than a tiny cam, and designed for single plug. Bigger engine needs more camshaft relatively speaking. It reads that you don't need to pass emissions so fit something decently sized for a cam, that the engine designer has known works for this combo at your(I suggest) 9.7-9.8 : compression for single plug. My guess would be a Mod Solex grind as a candidate, I have overdone this choice on a recent 3.45 L w 3.2 motronic and went backwards as it lost power Vs upgrade 1 , when I upgraded to another level on cams, not LOL. A 993 SS may be too light I guess , meaning not enough valve open duration ...

This engine will absolutely need a custom calibration when assembled to drive nicely throughout the rpm range, and be safe at WOT power levels.

Heard Spa 6 Hour WEC race is on so time to go waste away an hour or two seeing how that is going!

Good luck
Kevin
GAS Motorsport

[LT86]

Injectors: clear! I'll ask the shop what they use (they've build many engines with great reputation). If not I'll get back to you.

No go on 100mm bore for stock setup: clear!

Rods: they're not stock. I'll the put the link here of the ones I'm buying.

There are no emission tests so on this one I would be free to do what I want. However, I want to keep the heating so not sure if there is a higher performance option which still retains this. I'll find out.

Again, good stuff. Learning a lot, thanks!!

[LT86]

hi everyone,

Thought I'd give an update as many of the parts arrived and it might help someone trying to find info on a similar setup. Starting from my 3.2l and upgrading to 3638cc (3.7L).

Parts list:
- Light flywheel
- SCART Riva sport muffler
- 80.4mm GT3RS 4.0 spec crankshaft
- 3.0 Mittelmotor racing rods (576gr. a piece) and ARP bolts.
- JE custom pistons (425gr. and 110gr. for the piston pen)
- Bored MAHLE 98mm cilinders.
- Mittelmotor Motronic Sport Camshafts. Maximum valve lift is 12.4 mm (original 11.5 mm), 3.0 mm inlet valve lift with overlap.

I'm still running the original 3.2 injectors but these will not suffice. I've read that LUCAS injectors are a suitable alternative (LUCAS DB1540BA or D1610BA) but will contact Kevin after checking with Steve Wong on the chip.

Also reading up on upgrading the oil pump. The car will see mostly street but some track as well. Not sure if a 964 pump would also be good nor if a gt3 one would be overkill. Need some more Pelican time .

At the moment I'm running the FVD MAF KIT with a chip. But FVD are not able to adjust my chip for the new setup as it's matched to the MAF kit so I've reached out to Steve Wong. He recommended to remove the MAF kit, go for the original factory air flow meter and then have a chip made by him.

Pictures are not showing up for some reason.

[stownsen914]

Did he recommend removing the MAF because it’s not a good unit, or because he doesn’t have a way to account for it in his tuning? The stock intake will be a significant restriction for your build, I’d have thought a MAF would be a good upgrade.

[LT86]

Originally Posted by stownsen914

Did he recommend removing the MAF because it’s not a good unit, or because he doesn’t have a way to account for it in his tuning? The stock intake will be a significant restriction for your build, I’d have thought a MAF would be a good upgrade.

Personally I was happy with the MAF kit but according to Steve it has nothing to do with the kit itself. It's the chip that makes the difference.

Their MAF requires their own proprietary chip to make the sensor work, and is not compatible and will not work with any chip designed for the factory air flow sensor. I am not able to make a chip for their kit.My recommendation is to remove the MAF kit and go back to the factory air flow meter and then I can provide you the proper chip. Extensive dyno testing comparing the factory sensor with a aftermarket MAF sensor, such as the Bosch HFM element in the FVD kit, on 3.2s and 964s, show no HP gain from a MAF sensor, not even 2 hp at 7000 rpm at full throttle. So it is a waste of money. Also many 964 owners and engine builders contact me about helping to fix all the various drivability and running problems they have with their FVD MAF kit, in which I strongly recommend they remove it and return back to the factory air flow meter, and l provide the proper chip for their car, after which all the problems go away the car drives smoother and flawlessly and makes more power than ever. If you ask FVD to build you a custom chip for your engine build below, they will not be able to do if, and if they say they can I would not believe it.

I have not found a single company who can change the map I have so I trust Steve in his experience. Would like to go for intake mods as well but local DMV would not allow for it and take the car of the road if spotted.

[stownsen914]

It’s possible that MAF is different. I’d always understood that a MAF flows better than the standard throttle body and was better at metering the air.

[ericwitte]

Speak with Sal Carcellar. His MAF and injectors upsize well


Sent from my iPhone using Tapatalk

[stownsen914]

Just ran across another thread claiming no significant ho increase from a MAF in back back tests. Sometimes you have to just go with what the experts tell you.