compression ratio

[Catamax944]

My engine is due for a rebuild soon and i will be doing a few upgrades.
One of the upgrades will be wossner pistons and the new high compression pistons that lindsey are selling look very attractive.
Other upgrades to support this will be a high lift cam but nothing too crazy and standalone ecu .
My question is how much can i raise the compression ratio without losing driveability , the car being mostly a daily driver with little track use.
Would 12:1 be realistic with 94octane (100 RON) ?

[wildcat077]

Most 944 Spec race cars safely run with 10:6:1 compression ratios on 94 octane fuel without detonation ... i'm guessing that 12:1 would require 104 octane and an adjustable fuel pressure regulator with some dyno tuning !

Cheers
Phil

[v2rocket_aka944]

sounds like a good project!
you may want to consider adding the low-temp thermostat and low temp fan switch to try and keep coolant cooler to help prevent detonation

[Catamax944]

My car is euro so 10.6 is stock , never had any detonation problems with any kind of gas.
I will talk with my tuner before building the engine but untill then i would like to learn a few things from other people experiences.
The best gas availabe to me is 100ron and since the car is mostly street i need to find ot the limits of this engine based on that.
Interesting about the coolant temp , thanks for the tip ,i didnt know about that.

[blade7]

Will you be using the 968 block ?

[9FF]

Save yourself a bunch of money, time and headache. You already have the Euro hc pistons, for a street car I would just get the na-tune, maf and advance the cam with an offset key.

[H.F.944]

Originally Posted by 9FF

Save yourself a bunch of money, time and headache. You already have the Euro hc pistons, for a street car I would just get the na-tune, maf and advance the cam with an offset key.

nice advice, hm, isn't na-tune already using a MAF? So why should he just get another MAF?

[H.F.944]

Originally Posted by Catamax944

My engine is due for a rebuild soon and i will be doing a few upgrades.
One of the upgrades will be wossner pistons and the new high compression pistons that lindsey are selling look very attractive.
Other upgrades to support this will be a high lift cam but nothing too crazy and standalone ecu .
My question is how much can i raise the compression ratio without losing driveability , the car being mostly a daily driver with little track use.
Would 12:1 be realistic with 94octane (100 RON) ?

Nice project, as far as I know the 944 (Euro 10.6 CR) is not very knock sensitive. But to raise the CR from 10.6 to 12.0 won't make that much extra hp. With a well tuned standalone ECU and 100RON, driveability shouldn't be a problem. The pistons you mentioned are up-to-date pistons. Very light, short skirts and new ring technology for better sealing and thus nearly no blow-by. These new and light pistons alone should make some noticeable difference apart from the raised CR.

Attached is the blueprint of my rebuild. I don't care the effort; it's my hobby. 2.9l stroker.
S2 Crank, Chevy Pistons, Light Weight 150mm Custom Rods. Standalone ECU (with MAF).

[9FF]

Originally Posted by H.F.944

nice advice, hm, isn't na-tune already using a MAF? So why should he just get another MAF?

Yes the na-tune includes a maf, should have made that clear in my post. A lot of work went into the system and it has proven results, plus it's relatively cheap and plug and play. Going standalone to try and tune in a few extra hp is a waste of time and money imo on a street car. Same with hc pistons or a hl cam, just too much expense for the small increase in hp.

Having said that I do run TechGT with DFU's and sequential on my one of my na cars that has the 10.6 Pistons and its a great system but was not cheap and took a lot of dyno time to get right.

[Catamax944]

Unfortunatelly i cant use the 968 block as i have to keep the factory engine code in order to keep the car street legal .
My wish is to build the most extreme street 8v n/a engine possible , i wont be happy with just na-tune and i dont want 16v , budget is always an issue of course but what i have is patience ,it will be a long term project ,one year or more.
First i will gather all the parts i need and document all that i can then i will start the build.
My build list so far is as follows
Parts that i have
-968 crankshaft -needs to be modified
-968 oil pan - also to be modified
-968 headers ,cat and resonator all stainless - will send soon to have 8v flanges welded on headers ,i need to install it before the build because because the stock one is cracked
-951 head - needs to be ported intake side
-Michael Mount valve springs
-Lindsey adjustable fuel regulator
-968 radiator- installed
Parts i need to get
-augment automotive camshaft
-augment automotive ECU or Haltech sprint 500- not sure yet which one
-968 TB or bmw S14 ITBs -also unsure
-RC injectors
-Rarst rods with Michael Mount bearings
-lindsey oil pan baffle
-crank scraper
-arp hardware
-custom wossner pistons

On a side note very promissing progress is being made on my 01E conversion but i wont get into detailes untill its finished.

[Catamax944]

So you are going with Sids stroker design , very nice!
What ECU will you be using
The problem i have here in Italy is sleeving the block , its hard to find anyone with experience in alusil blocks. Where are you getting your work done?

Originally Posted by H.F.944

Nice project, as far as I know the 944 (Euro 10.6 CR) is not very knock sensitive. But to raise the CR from 10.6 to 12.0 won't make that much extra hp. With a well tuned standalone ECU and 100RON, driveability shouldn't be a problem. The pistons you mentioned are up-to-date pistons. Very light, short skirts and new ring technology for better sealing and thus nearly no blow-by. These new and light pistons alone should make some noticeable difference apart from the raised CR.

Attached is the blueprint of my rebuild. I don't care the effort; it's my hobby. 2.9l stroker.
S2 Crank, Chevy Pistons, Light Weight 150mm Custom Rods. Standalone ECU (with MAF).

[v2rocket_aka944]

Originally Posted by Catamax944

On a side note very promissing progress is being made on my 01E conversion but i wont get into detailes untill its finished.

i would be very interested in knowing these details when they are available.

there is power to be had in the 944 8v, you just have to dig for it!
get the head ported properly and increase the displacement as much as possible.

as a variant of the "hybrid stroker" you can offset grind the 2.5 crank to 1.889"/48mm, use the factory 944 pistons and eagle connecting rods for a GM Quad-4 engine. it will give you about 0.12L more displacement but is cheap enough to consider. it would drop your compression ratio just a little bit though because the pistons would not be coming quite up to the deck anymore but that would give you some safety margin.

if you are using a 968 crank then you would need to have a piston made with that diameter and pin height.

[9FF]

Originally Posted by Catamax944

Unfortunatelly i cant use the 968 block as i have to keep the factory engine code in order to keep the car street legal .
My wish is to build the most extreme street 8v n/a engine possible , i wont be happy with just na-tune and i dont want 16v , budget is always an issue of course but what i have is patience ,it will be a long term project ,one year or more.
First i will gather all the parts i need and document all that i can then i will start the build.
My build list so far is as follows
Parts that i have
-968 crankshaft -needs to be modified
-968 oil pan - also to be modified
-968 headers ,cat and resonator all stainless - will send soon to have 8v flanges welded on headers ,i need to install it before the build because because the stock one is cracked
-951 head - needs to be ported intake side
-Michael Mount valve springs
-Lindsey adjustable fuel regulator
-968 radiator- installed
Parts i need to get
-augment automotive camshaft
-augment automotive ECU or Haltech sprint 500- not sure yet which one
-968 TB or bmw S14 ITBs -also unsure
-RC injectors
-Rarst rods with Michael Mount bearings
-lindsey oil pan baffle
-crank scraper
-arp hardware
-custom wossner pistons

On a side note very promissing progress is being made on my 01E conversion but i wont get into detailes untill its finished.

That is a very ambitious build, definately be following your progress. It's a shame you don't have anyone over there who can sleeve the block, I'd really like to see someone build a big bore 3.2 8v na. ITB's are a nice bling factor and bragging rights I doubt they are beneficial until the upper rev range though and would be a pig to set up consistent vacuum and idle for a street car. Would it cost too much to crate your block over here to fit 108mm wet sleeves? Just saying, to get the hp without increasing cubic capacity is a lot more expensive.

[H.F.944]

Originally Posted by Catamax944

So you are going with Sids stroker design , very nice!
What ECU will you be using
The problem i have here in Italy is sleeving the block , its hard to find anyone with experience in alusil blocks. Where are you getting your work done?

Yes, it's Sids design applied to a 944 N/A.
ECU will either be augment automotive ECU or megasquirt.
Regarding Alusil, I've already talked to AWS GmbH, Hamm/Sieg and Eberhard Hoeckle GmbH, Mössingen. They said no problem. AWS offer their services even on Ebay.de (Ebay-Username: blaumaenner).

[H.F.944]

Originally Posted by v2rocket_aka944

...

as a variant of the "hybrid stroker" you can offset grind the 2.5 crank to 1.889"/48mm, use the factory 944 pistons and eagle connecting rods for a GM Quad-4 engine. it will give you about 0.12L more displacement but is cheap enough to consider. it would drop your compression ratio just a little bit though because the pistons would not be coming quite up to the deck anymore but that would give you some safety margin.

if you are using a 968 crank then you would need to have a piston made with that diameter and pin height.

don't forget, the 944 rod pin ID is 0.944" vs. Chevy 0.927" vs. Mitsu/GM 0.866".
So you'll have to press very hard to get the factory 944 piston pin into the Chevy or Mitsu/GM pin hole.

[v2rocket_aka944]

Originally Posted by H.F.944

don't forget, the 944 rod pin ID is 0.944" vs. Chevy 0.927" vs. Mitsu/GM 0.866".
So you'll have to press very hard to get the factory 944 piston pin into the Chevy or Mitsu/GM pin hole.

here's the rod in question, they sell a set of 4 as well.
http://www.summitracing.com/parts/esp-5806c3d-1/overview/make/oldsmobile

and there is enough meat in the rod end to bore it to 944 size without worry

[H.F.944]

Originally Posted by v2rocket_aka944

here's the rod in question, they sell a set of 4 as well.
http://www.summitracing.com/parts/esp-5806c3d-1/overview/make/oldsmobile

and there is enough meat in the rod end to bore it to 944 size without worry

Ok, a dremel would do the job for the do-it-yourselfer easily.

[Catamax944]

Originally Posted by v2rocket_aka944

here's the rod in question, they sell a set of 4 as well.
http://www.summitracing.com/parts/esp-5806c3d-1/overview/make/oldsmobile

and there is enough meat in the rod end to bore it to 944 size without worry

That price is per rod right ?
The eagle mitsubishi rods are on sale right now ,very tempting https://www.raceeng.com/p-24675-eagle-h-beam-rodmitsubishi-4g63gen-1for-22mm-pi-set-crs5900mc3d.aspx
Those are the cheapest solution right now
In my situation i think i have to minimize cost for machine work more than i have to on parts. Or at least that is my logic untill i find a good machine shop.
The 968 crank i have is leftover from a 968 engine i dismanteled , its new 0 miles but had water exposure for many years and the journals are rusty. A build like this is the only way to use it , most likely i will have to use oversize main bearings and oversize rod bearings or offset grind it. I was hoping not to offset grind it in order to keep the cost down.
As for pistons my mind is pretty much set on wossner , i didnt see any good chevy pistons signifficantly cheaper....

[Catamax944]

Originally Posted by 9FF

That is a very ambitious build, definately be following your progress. It's a shame you don't have anyone over there who can sleeve the block, I'd really like to see someone build a big bore 3.2 8v na. ITB's are a nice bling factor and bragging rights I doubt they are beneficial until the upper rev range though and would be a pig to set up consistent vacuum and idle for a street car. Would it cost too much to crate your block over here to fit 108mm wet sleeves? Just saying, to get the hp without increasing cubic capacity is a lot more expensive.

One local shop i asked said its no problem ,they sleeved merc V8s before but when i mentioned alusil they were cluless to what it was and said they wont assume any responsibility for this kind of work although they also said it will cost me 250euro a sleeve. How can i trust someone like that with any kind of engine...
Yes the reason i even considered ITBs was the bling factor and sound and the fact that there is for sale 20min away from me a bmw S14 set ported and complete with plenum and gaskets . But like you said there a pig to set up and make power only up top . My goal is to have drivebility close to stock and lots of low end power and torque . In the end im pretty sure i wont be using ITBs even though im drooling when i think about them .
Not sure i will consider wet sleeving it because its pretty high cost , its more probabile it will be dry sleeved ,max bore for dry sleeved 2.5 being 106mm.
From my experience with shipping to and from US i estimate about 1k cost back and forth.

[v2rocket_aka944]

Originally Posted by Catamax944

That price is per rod right ?
The eagle mitsubishi rods are on sale right now ,very tempting https://www.raceeng.com/p-24675-eagle-h-beam-rodmitsubishi-4g63gen-1for-22mm-pi-set-crs5900mc3d.aspx
Those are the cheapest solution right now
In my situation i think i have to minimize cost for machine work more than i have to on parts. Or at least that is my logic untill i find a good machine shop.
The 968 crank i have is leftover from a 968 engine i dismanteled , its new 0 miles but had water exposure for many years and the journals are rusty. A build like this is the only way to use it , most likely i will have to use oversize main bearings and oversize rod bearings or offset grind it. I was hoping not to offset grind it in order to keep the cost down.
As for pistons my mind is pretty much set on wossner , i didnt see any good chevy pistons signifficantly cheaper....

my suggestion above lets you re-use the stock pistons but still get more stroke because the rod is a little shorter. still plenty-high rod/stroke ratio if you're concerned with that. but again, just a suggestion but either way you've got a cool goal in mind!