I'm thinking of mild port and polishing my 944 turbo head?

[Dan944t]

hi guys ,

in winter I'm going to be making the time to finally totally rebuild my engine as some of you may know already.

ive got quite a few mods to the car already which I'm very much looking forward to seeing the results, and in doing all this work I've been seriously considering doing a mild port if needed? And polishing job on my head?

i have already started to hone out my inlet manifold as i took a look inside as I ceramic sprayed it , in preparation for the rebuild when cleaning things up, and to be honest I was horrified at just how appalling the casting was inside and the differences in each passage to feed each cylinder. I took a hell of allot of spicky rough cast of along with uneaven cast line/ridges and have high hopes that I will pick up a nice bit of flow her. I have loads of before and after photos but I need to sighn up to a new host sand learn how to put them in here before I can post.

my question in advance is: has anyone got any experience in porting or polishing out the bowls ect on this head and do you think there is any gains to be had.

I personally think there is as I can't see why not if things are done correctly and not ruined, even if it's just to maybe keep it cleaner from carbon deposits for longer? I don't know I thought I'd ask if anyone had first hand experience in this. As the only other people I know who do this to this model is the Lindsey
Racing heads that are pre port and polished along with there type manifolds , but I'm only interested in doing a mild job to this one, and not interested in buying one of those.

im also thinking of making a DIY flow bench which will be accurate enough to monitor the gains in flow enough to replicate before and after in different levels of the valve opening, so I'm thinking maybe this could be wirth my while and time?

Look forward to any advice or knowledge?

all the best
Daniel ??

 

[924Srr27l]

2 Options:

1. tinker yourself
2. Send your head or another one to Lindsey

Option 1 could be fun if you mad keen to have a go but prepare for issues and a potential loss
The people that have decades of experience and guaranteed results are not to be ignored as option 2

With a mildly different camshaft profile and a honed inlet manifold and Lindsey stage 2 head I got 40bhp more
on a 2.7 motor compared to the OE Porsche model.

R

 

[John Sims]

My understanding is Porsche did a sound job in the first place and the gains would be negligible. As such, unless it is desperately dirty I wouldn't bother personally.

 

[PSH]

I have an LR stage 2 with a few added options...I changed the valves though after having number 4 melt due to, I assume going a little lean, although I didn't notice anything wrong with the AFR at the time. Drove approx 40 miles home on 3 cylinders...lol Part of the work that Lindsey do to increase valve opening involves machining the valve lip down to imho far too thin a profile, I've had no repeat since reprofiling the seats and fitting standard valves.
IMHO a polished head does make a difference although be careful on how far you go, there's some debate about too smooth a bowl effecting atomisation... I'm on the side that supports the need for a slightly rough service to help mix the fuel/air properly... there's plenty of articles on the web to help you make your own decision though...

cheers

Pete

Pete

 

[blade7]

My understanding is Porsche did a sound job in the first place and the gains would be negligible. As such, unless it is desperately dirty I wouldn't bother personally.

This^^^^ especially on a turbo.Though If you really must have a go, just blend the throat area into the valve seat. And it's vital to use a quality dust mask and eye protection.

 

[Dan944t]

thanks so far guys for your comments I appreciate them All!

i was originally thinking bigger valves but at this point I'm not going down that route and am going to keep the valves standard as they have All been cleaned and checked by Jon. All I was intending to do was a little mild de casting and smoothing out of the throut as blade says and slightly bullet nosing around the valve guild but I wasn't planing to do any drastic changes, even though to most it may seem a bit drastic but I'm always in the mindset that unless it's a custom job there always gains to be had. Im not the type to be scared of things like this and am handy with the tools and have a good steady hand and am used to sculpting out of wooden blanks so feel I could do it justice, as I'm planning to do anything crazy. But I would like to further inspect inside inlet ports when I pick up my head and I will have a good think whikst it's in front of me. Just putting feelers out to see if anyone had experience with this head. I understand things are a little different becuase it's a forced induction head and engine which is actually why I thought it could also aid to an advantage becuase of being able to tune the air and fuel far more than a non asperated model. ... but as there's hardly anything on doing this to this sperciffic engine, thought I'd ask for any thoughts before I do.

as said before the thing that got me thinking about there's possibly a big improvement to be had ( possably?) is how bad porsche had left the inside of my inlet manifold which if I'm totally honest and not exaggerating, if I put my fingers inside and dragged them along the inside cerface and out, I would have drawn blood and scored up all my skin, so that's why I got to work on that which isn't easy becuase of the access as in enters deeper but i made some custom tools up and lots of elbow grease and before the house moove I would say I got maybe 90% through that job. once done and fitted I know for sure that that will be breathing minimum of 30% better and therefore gains to be had.

if I wasn't literally having to build the engine up from scratch as I'm having to do, I don't think it would even cross my mind as I was happy as it was, but being in my situation now which hasnt been easy in a number of ways, I feel like I want to have a go whilst putting all this hard work, time and money into this engine build to do something whilst it's in front of me and possible, as long as it would be worthwhile ?

Daniel

 

[blade7]

You could have cut the inlet manifold in half, flowed it, and then welded it back together. Or constructed a new plenum with bellmouths, but people have made 400 bhp with the standard manifold...

 

[924Srr27l]

i was originally thinking bigger valves but at this point I'm not going down that route and am going to keep the valves standard as they have All been cleaned and checked by Jon.

All I was intending to do was a little mild de casting and smoothing out of the throut as blade says and slightly bullet nosing around the valve guild but I wasn't planing to do any drastic changes,

as said before the thing that got me thinking about there's possibly a big improvement to be had ( possably?) is how bad porsche had left the inside of my inlet manifold which if I'm totally honest and not exaggerating,

I feel like I want to have a go whilst putting all this hard work, time and money into this engine build to do something whilst it's in front of me and possible, as long as it would be worthwhile ?
Daniel

I think you need to make a decision what you really want? Your title questions says the word "MILD" but then you also mention in regard to the inlet manifold inner surfaces a BIG improvement may be possible, also the BIG valve thoughts have come and gone
and then you've said that a lot of money has gone into this engine etc...so surely you either do it properly or you leave it as is ?

Only there isn't as such a half way house mild amount of work that you will notice any difference from the cockpit.
This is my opinion and I spent a lot of time and money and got a 37% increase from my original engine power which was and
is a sizable chunk to make a big difference but of course the weight loss programme made the power to weight increase from
119bhp per ton to 200bhp (A increase of 68.2%) again I did't just remove 100kg but 250kg to create the biggest effect possible.

If I had to do it all again on another big project i would follow this same template, all or nothing or don't bother.

The Increase in CFM for the Extrude Hone Inlet manifold I had done in the USA is quoted at +25%
The lindsey stage II Port work increases by 28% CFM. So you can imagine if the airflow after the throttle body is able
to flow more by 25% and the cylinder Head also a slightly higher figure then combined with my higher Duration Camshaft and Turbo
Exhaust Manifold (Plasma Coated) and the important mapping the motor produced 40bhp more than a stock 2.7.

R

 

[Dan944t]

You could have cut the inlet manifold in half, flowed it, and then welded it back together. Or constructed a new plenum with bellmouths, but people have made 400 bhp with the standard manifold...

I would love to make my own up, maybe one day when I brush up on my welding skills but it would be quite a job .

But would take it on in the future if it was well worth the effort. All beit with another second hand item to cut up and not this one so that I could bolt off bolt on!

i think there's allot to be gained by the inlet and head that we don't seem to hear much talk or nodding about these apart from linsey racing? Maybe becuase of the power levels that it would benefit which we all know the Americans are used to far more power than us in the uk. We tend to be happy in the 300 area where as they go silly high, maybe that's the reason behind it.

i was told by a racing team whilst trying to sorce who could fix my split cylinder, that they looked after a customers race 944 turbo with all the lindsey racing bits and bobs on, and I asked what they thought if there racing inlet manifold they sell which was in this spercific race prepped 944 turbo running 380bhp and they said it was a pile of S@@T so I didn't ask any more about it, which now I wished I did. It seems to have maybe too much space inside before the passages to the cylinders if I remember right?? ( but could be wrong) so maybe these are designed for larger turbos with 20 + psi if boost to cope and make sense of the modification different volume inside ??? It's all a science which if I understood and could mathematically understand 100% I would be laughing but as I don't I will tinker as much as I understand and hopefully gain a bit of benefit from what I do understand.

atb
daniel

 

[John Sims]

The Increase in CFM for the Extrude Hone Inlet manifold I had done in the USA is quoted at +25%
The lindsey stage II Port work increases by 28% CFM. So you can imagine if the airflow after the throttle body is able
to flow more by 25% and the cylinder Head also a slightly higher figure then combined with my higher Duration Camshaft and Turbo
Exhaust Manifold (Plasma Coated) and the important mapping the motor produced 40bhp more than a stock 2.7.

But this is for a N/A which is completely different to a Turbo. A N/A will suck the air into the cylinder and any increase in flow will assist this. A pressurised turbo will pummel the air into the cylinder with great big boots. The air has no chance of meandering in the inlet manifold as it is going into the cylinder as soon as the valve creates a gap. When you consider the air has already been on a sight seeing trip of the inside of the inter cooler a few nodules in the inlet manifold will have almost no bearing on anything.

If you are running 1 Bar boost your 2.5 ltr engine is having 5 ltrs of air whether it likes it of not. If you consider modern turbo manifold installations they have all manner of strange chambers which will do nothing for air flow but are (I assume) there to buffer the harmonics of the air when the valve closes and the air being pushed from behind finds it has nowhere to go.

 

[924Srr27l]

The Increase in CFM for the Extrude Hone Inlet manifold I had done in the USA is quoted at +25%
The lindsey stage II Port work increases by 28% CFM. So you can imagine if the airflow after the throttle body is able
to flow more by 25% and the cylinder Head also a slightly higher figure then combined with my higher Duration Camshaft and Turbo
Exhaust Manifold (Plasma Coated) and the important mapping the motor produced 40bhp more than a stock 2.7.

But this is for a N/A which is completely different to a Turbo. A N/A will suck the air into the cylinder and any increase in flow will assist this. A pressurised turbo will pummel the air into the cylinder with great big boots. The air has no chance of meandering in the inlet manifold as it is going into the cylinder as soon as the valve creates a gap. When you consider the air has already been on a sight seeing tip of the inside of the inter cooler a few nodules in the inlet manifold will have almost no bearing on anything.

Turbo Heads also John, it's the same if you can only get so much air through (Cubic Feet Minute) and modifications will allow more
air through then the extra amount (volume) and speed (faster flow) can be adjusted with mapping to produce more power and Torque...


CFM Increase
Stock1802223Level I1863 %Level II23228.8 %Level III25239 %

R

 

[Dan944t]

Hi Roger,

to to answer your question: as I said I had thought about bigger valves but have decided not to for now and do some mild porting and polishing for now as if I wanted I can always wip my head off and do a valve job to it and I will already have my porting and polishing already done, which is my goal in doing so. In mild porting and polishing I mean that I'm not looking to go crazy as I said preveously, in that I mean I'm not looking to take loads of meat from my bowls which would change my compression ect, I'm just thinking of some mild tunning as I'm taking out some casting marks/ lines and maybe bulleting the shape around the valve guilds if I feel I would benefit I. Flow there, and some polishing in certain areas but not a mirror finish, I'd like to leave a slight swirl but smoother than is there already, and if I see any sharp edges or something I think I can improve flow wise I will do it.

Just to add, just incase you was under the impression I'm thinking of doing this to a standard engine? I'm not I already have spent £10,000 on mods alone that's on top of the cost of the total rebuild in about to complete in the winter fingers crossed.

this is the set uo so far:

original cylinders milled away, and .05mm larger custom race wet liners installed Woodford/serdi

IASA race pistons and rings serdi

race conrods custom made for me from a race firm in millan through serdi uk

polished crank serdi

lightened flywheel serdi

crank scraper

larger 9xx 55 lb injectors JMG

38mm Tial dual port wastegate
JMG

manual boost controller JMG set up for 18psi

JMG quite agreasive but very nice chipset from mr Mitchell for my set up of mods

AFM reconfigured by mr Mitchell

3 bar fuel preasure regulator

aftermarket boost gauges

uprated vacum lines JMG

Upgraded bigger intercooler JMG

larger capacity motorsport fuek pump JMG

heat wraped turbo downpipe, and exhaust downpipe.

993 recirculating valve

K&N air cone ( which is like to box in near incoming wing air tube)

new bearings/ rollers/waterpump ect ect

APR head stud and bolts serdi

short block and head mating serfices have been made to be welded and flattened by serdi uk to a mirror finish.

Steam vent fitted in back of head to try keep heat down by dispersing trapped bubbles.

crank, pulleys flywheel ect have all been balanced together

Rear sports exhaust with straight pipes to the front box.

thats most of the engine side but I've most probably missed stuff but as you can see, I have made my dicision in the direction I'd like to go, and my thoughts are by doing a bit of mild port and polishing as I've said above, my thinking is im only setting myself up for the future mods which I can inteoduce at a later date such as :

larger turbo?
stand alone set up?
vitesse air maff kit?
set up by the wizard ( this one is a deffinate)
larger valve job/different cams

and so to be honest apart from upping the litre which I've no intension of doing now I have a rock solid bottom end , I think with a bigger turbo ect this could potentially be quite a car.

appreciate your comments as always

Daniel

 

[PSH]

an impressive list Daniel...I would say, think about using an adjustable FPR rather than one set at 3 BAR, fit a gauge to it too so that you can check the pressure easily if experiencing any problems with the car such as lean AFR, slow pickup etc. I set mine at 3BAR anyway but have adjusted this both up and down when the AFR has given the wrong readings, it makes me feel safer knowing that I can fine tune the pressure for any given situation.
Wayne (wizard) is most certainly the guy to see, he added me as a friend on FB a few days ago after he answered and supported an opinion I was trying to explain to 996 owners regarding their engine issues...actually it effects 996, 987, 997 1st gen, Cayman etc...Porsche just don't build them like they used to...

On another subject altogether Wayne was telling me about being called in by Porsche to fix a problem on a GT1, they couldn't work it out themselves,,I said nice car but not my thing...so he told me he was also called in to look at a 924GTP...now that's much more up my street....I have no doubt that Wayne's magic will transform how your car drives...I still need to sort out another session with him myself ..one day...

Pete

 

[Dan944t]

Hi Pete ,

not sure about impressive, but I sure have been bitten by the bug since andy at Promax unleashed the potential when I bought a boost inhancer from him many moons ago!

Im glad I did just wish I did it all when I first rebuilt the top end, but as we all know these things demand a lot of money and if i wasn't hands on as a few of us are I would t be able to afford to get all these mods fitted at this point in my life with kids and all.

regarding the adjustable fuel regulator, this sound like a good thing. only thing I'm thinking is, is this the type that has the glass gauge in the engine bay?

atb
daniel

 

[PSH]

Hi Pete ,

regarding the adjustable fuel regulator, this sound like a good thing. only thing I'm thinking is, is this the type that has the glass gauge in the engine bay?

atb
daniel

Yes...I wouldn't like to have one in the cab... you can either fit it to the end of the fuel rail or to the FPR itself, which is where mine is fitted.

cheers

Pete

 

[Dan944t]

I've always been worried about fitting these just incase of a leak in the glass? Is that just me being paranoid?

I heard it happen once to to a guy with a 928 and its always been in the back of my mind as once on my lux the fuel rail split as I was driving and you can imagine what happened after that. I was lucky.

is this just maybe a cheap item that this guy might of had?

Is this the only gauge available in the rail? I'm sure that's where it had to read it the best allot like when I mooved the lines to read my boost preasure more accurately but I dont have any knowledge of this item.

I take it that it is a manual adjustment inside the engine bay whi the car is on and thus pressurised or am I wrong?

sorry for the questions mate, seems so many when you have to physically ask in writing!

cheers
daniel

 

[PhilKent]

Hi Daniel, read the thread with interest. Your mods are a great start for a strong engine and regards the porting, when I re-built my engine I simply ground out the exhaust/inlet ports to match to the manifold so I can't give REAL advice here, but matching the inlet/outlet to the manifolds I think is always a good idea, I tend to go with the theory that a rougher finish on inlets (resulting in a bigger boundary layer and hence a slightly lower effective area for the inlet, but still only talking microns) gives a better opportunity to mix the fuel/air unless you are going for all out high revving hi-flow performance.
As regards your other mods, since you are bitten by the bug, I would recommend considering an after market ECU to manage the fueling as you carry out further mods. It'll help your wallet in the longer run too as you won't need to get custom chips and maps for every mod you do (eg, you won't need an adjustable FPR as you can manipulate the fueling within the software). David and I have both gone for VEMS stand-alone ECU's which are a 'backwards compatible' product. i.e. you can reverse everything by simply un-plugging if you wanted to.
It's worked brilliantly for me and as I carry out further mods such as my recent intercooler DIY mod I can record and note the differences.

Best of luck with the mods and I only wish I had the budget for such a fancy bottom end when I was re-building my engine!

 

[PSH]

no need to apologise Daniel...I ask questions too when I need...in the early days, I asked many believe me...

I thought the easiest way to explain, was with a picture...I struggled to get the phone low enough to get a clear view of the gauge but rest assured it's easy to read in person. The adjustment is via the dome nut next to the vac line, you remove this nut, below it is the normal locking nut, slacken this off and there's a screw with a slot for a flat head screwdriver. You turn this to adjust the pressure, hold it in place with the screwdriver and tighten the locking nut, last job being just to replace the dome nut ensuring that you don't disturb the nut below. I adjust the pressure with the engine running, it takes just a minute or two. IMHO it's a good thing to have, I was on holiday in Wales one time when the AFR was giving me strange readings and the car wasn't feeling right, down on power. I adjusted the pressure a little and cured the AFR problem until I was back home. I can't remember what the issue was now...funny how my mind works these days, or doesn't should I say...lol

Pete

 

[PSH]

Hi Phil

Just read your comment re fueling...unless I'm missing something, fuel pressure and fuel management are two different things, I too, can fully adjust my fuel throughout the rev range via the piggyback on my laptop. I except that the VEMS seems like a good bit of kit and it's self-learn makes life simpler but would disagree that this negates the need for a map written by somebody who knows the ins and outs of such things, this is where Wayne is supreme, IMHO of course. I have adjusted my map myself, with my son's help I must add, to allow for the recent mods but I know that the car will not be performing to it's best potential until Wayne has done his magic, his experience in tuning engines of any type and most certainly the 951 is second to none.

regards

Pete

 

[PhilKent]

Hi Pete,

Afaik the main purpose of adjusting the fuel pressure is to change to fueling, i.e. alter the AFR in a car that does not manage its AFR 'on the fly'. Of course you need good pressure to atomize the fuel through the injectors, but in and around 2.5-3.5 bar pressure is what the injectors are designed to handle.
My comment regards an ECU that 'automaps' the fueling is that you remove the need for this alternative method of manually adjusting that AFR. I agree you cannot expect an 'automap' to give as good a result as an experienced engine mapper, but it is designed to give as close to stoichiometric efficiency as electronically possible, which will be a damn site closer that you can achieve by adjusting the fuel pressure manually.
If I were to add an adjustable FPR to my set-up the ECU would then 'notice' (if I run the software) a change in the combustion gases and adjust the duration of the injectors to offset that change in fuel pressure.
By the way, this wizard you speak of, where is he based, and is he familiar with VEMS ECU's? I need a good mapper...