Turbo mods

[poprock]

ORIGINAL: DavidL … you pay much more for far smaller gains as you go up?

That’s my understanding of it, in a nutshell. Eventually, the law of diminishing returns kicks in.

 

[Suffolk944]

Yes thats how it works I am afraid ! It's why I have not (yet) gone for a full L3/S3 kit as I struggle to see how the much higher cost of such kits can be justified for road use, especially here in the UK these days where the opportunities to deploy all that extra power either because of traffic levels or cameras is frankly pretty rare. If I shelled out an extra £2-£3k for another 50 HP I would want to be able to use it on a regular basis !! If I was tracking/racing then that would be a different matter, but for UK road use I honestly don't think that either the extra cost nor the extra HP of a S3/L3 kit is worth it. My L2 kit plus MAF and EBC gives more than enough extra performance and improvement of power delivery over the standard set up that I will ever really be able to use regularly on the road IMHO. Doesn't mean I will never go down the route a bigger turbo etc but its not as high on my list of priorities as it once was.

 

[DavidL]

I really must be missing something in my investigation:
TheS2 kits are offering 90% of the S3 kits for a lot less than half the cost - both torque and horsepower

320 BHP - 375 lbs of torque - S2 kit - £1200 ish
330 BHP - 385 lbs of torque @ 2800 rpm - S2 kit plus a new turbo at £1000 extra

Add a MAF kit at £1500 and you get 360 BHP, 400 lbs of torque
(250 cars)

These are figures are lifted from a well known garage but I'm not making an example of them (I'd like all of it!) but LR, Promax, JM all give similar ish figures for similar packages and prices.
Now they are all a good chunk higher than normal but do you really get so little for such a huge outlay or is it just the way it is and you pay much more for far smaller gains as you go up?

I'm confused!!

David

 

[sawood12]

The stage 2 kits tend to focus on mapping and squeezing a bit more boost pressure out of the turbo. Quite simple really - the low hanging fruit of modding. What they tend to produce is more power and torque but all at the top end due to the mechanical constraints of the stock hardware. The Stage 3 kits address that - so yet again homing in on headline power and torque figures is only telling you a small percentage of the whole story. If you drove a stage 2 car and a stage 3 car back to back I think you'd be very surprised to learn they are very different animals despite their close-ish headline power and torque.

 

[Suffolk944]

All true but again for use on UK roads I just don't think you are able enough to reap the additional benefits of L3 kit to justify the outlay. That said as I now have everything for a L3 kit other than the new turbo its always at the back of my mind that I should really do it one day, just for the sake of completeness you understand ! []

 

[sawood12]

Jon, I agree which is why i've said before that you are far better off spending money on chassis mods - mainly suspension and brakes, as that will unlock real performance improvements that you can exploit in real world. I installed my Promax L2 kit before the KW and though I noticed an immediate performance improvement with the Promax kit it was limited to straight line blasts down dual carriageway slip roads and overtaking on A-roads. In terms of B-road getting from A to be B use the performance improvements were largely redundant as I was still on saggy 20yr old suspension and didn't ahve the confidence or skill to push any harder than before the Level 2 install. As soon as the KW's were installed it was really like stepping into another world, cornering speeds were significantly increased by 20 - 30mph on some bends known well to me when weather and traffic conditions allowed, and I could brake later and harder and get on the power earlier. The benefit of a new more modern turbo is not really the extra power and torque - it is the behaviour of the power delivery it brings. They will get on boost earlier, stay at max boost longer and performance will not drop off as aggressively when you get to the upper rev ranges. More power and torque will be available earlier in the rev range and you'll have it for longer. This will change the powerband from a more peaky stage 2 characteristic to a more mid-rangey and wider powerband. I'm not saying they are worth the money, but that is what the extra dosh will buy you. Personally the state I had my car in before I sold her was more than enough for my and my driving abilities. If I was doing more trackdays then I would have probably justified more spend on her - i.e. a Vitesse stage 3 kit, but for the road I think I hit a sweet spot with he Promax L2 kit, KW and Big Blacks. More power than you'll ever need and the suspension and brakes to take it.

 

[DavidL]

Thanks all. I think that has clarified my mind. As Scott says I can (almost) have a set of KWs and an S2 kit for the cost of an S3 (even the one I've been looking at) and that combination will almost certainly reap more rewards than the bigger turbo. My car will almost certainly not see a track so no gains there either. Thanks David

 

[DivineE]

Turbo tuning is literally what I spend my life thinking about, wasting money on. The trouble is as you aim for bigger figures more and more parts become problem points. Dependant on condition and which dyno you go to a standard 250bhp car with a chip, 3.0bar fuel pressure regulator and boost controller will produce somewhere between 290-315hp. This is because the standard injectors, turbo and air flow sensor are all at their maximum at this point. To go safely further than this you either have to go to a dyno for the day and get your car mapped to the modifications you have (because the air flow sensor is reading maximum flow but airflow is still increasing so fuel has to be increased manually based on RPM by looking at the mixture). Or like you say you can spend £1500 on a MAF sensor and pigyback. ..but there's really no point doing that without changing the injectors because they are at their maximum flow. The turbo also is getting increasingly inefficient at this point so is producing more and more heat which reduces air desity and so power. So then the rule is if you really want to go much over 300hp with a 944 you will need a lot more money to get those smaller gains. There is a slight cheat to be had though. I once went out in a car with just a chip that was running 311hp and 380ft/lb of torque. This is because torque isn't limited in the same way as hp by those components. Now that car was QUICK (I wonder if its still on here somewhere 'maroon' red' F** ***) and power was achieved by shimming the wastegate and bypassing the cycling valve so the wastegate control ran straight from the boost controller to the wastegate. Andy from Fernsport looked after the car so I'm sure its condition was good and it wouldn't have had any leaks but it had run that power for two years reliably on nothing more than a promax chip. I don't think you get a much quicker car without spending a lot more than the £2k you suggest and it is what has inspired me to have a go at the standard route this time.

 

[Diver944]

I think Scott has hit the nail on the head because the difference in the headline peak figures is not as dramatic as the extra urge and refinement you get throughout the whole rev range due to the MAF unit and modern turbocharger. It's those two pieces of hardware that really add the £1000's to the price over a simple chip and raised boost. I would always take the headline figures quoted by tuners with a pinch of salt but all of the above kits are similar in claim and price but they can't really show the huge difference they make to the driveability, extra response and reduction in turbo lag. It's only when you drive such a car that you realise the enormous leap forward that a better Turbo and MAF kit will bring you. The only grey area is whether you can justify the extra expense in your own mind [] For me it all boiled down to the fact that I love 944's. I love the useable 2+2 practicality, I love the huge useable boot and I love the balance and way the chassis handles. To get the same performance from another Porsche I would have to spend tens of thousands and move to a 996 or 997 era car which simply don't have the practicality I already have

 

[Suffolk944]

Yes indeed, my MAF has made a huge difference even with the standard turbo, I have just gone about the changes bit by bit as budget allows and then the expense doesn't seem so bad as it doesn't all arrive in one big lump ! []

 

[barks944]

Ive been thinking that i might got down the small ceramic bb turbo turbo route and getting spoolup as quickly as possible with the aim of producing massive torque at the low/mid rpm range and forgetting about high rpms. This way you would get a fast car without worrying about making the engine flow at high rpm. I think this would make best use of the charachter of an 8v engine which isn't suited to high flow rates at big rpm. Why go against the flow? Maybe boost by 2k and a 5krpm rev limit or something.

 

[TTM]

ORIGINAL: barks944 Ive been thinking that i might got down the small ceramic bb turbo turbo route and getting spoolup as quickly as possible with the aim of producing massive torque at the low/mid rpm range and forgetting about high rpms. This way you would get a fast car without worrying about making the engine flow at high rpm. I think this would make best use of the charachter of an 8v engine which isn't suited to high flow rates at big rpm. Why go against the flow? Maybe boost by 2k and a 5krpm rev limit or something.

The turbo is I think the part that will have the greatest influence on how an engine will feel from the driver's seat and yes, a bb turbo will be perform better than a non-bb turbo. I would avoid a turbo that is "too small" though, a GT30-based bb turbo should be responsive enough on a 2.5.

 

[DivineE]

ORIGINAL: barks944 Ive been thinking that i might got down the small ceramic bb turbo turbo route and getting spoolup as quickly as possible with the aim of producing massive torque at the low/mid rpm range and forgetting about high rpms. This way you would get a fast car without worrying about making the engine flow at high rpm. I think this would make best use of the charachter of an 8v engine which isn't suited to high flow rates at big rpm. Why go against the flow? Maybe boost by 2k and a 5krpm rev limit or something.

Totally agree but two points worth noting. First my friends skyline spat its ceramic turbo's down the exhaust when he raised the boost because they are not as tough as steel impellers so be careful and second I went out in a very well built car with exactly this set up built by RPM and whilst it would have undoubtedly be extremely hard to catch round a track the total loss of lag due to tiny modern turbo did lose a little of the cars character. It felt more like a modern hot hatch, which I'm sure some will consider high priase but I like the old bang and wallop, head sucked into the headrest feeling.

 

[poprock]

ORIGINAL: DivineE … I like the old bang and wallop, head sucked into the headrest feeling.

Here, here. That is exactly what I love about the 944 Turbo. I went for a passenger ride in my car before buying it and the first time I felt that moment of push was when the stupid grin spread across my face and I got my chequebook out. There’s no way I would intentionally smooth that lump of boost out of the power curve. It’s the whole point of the car for me. Without it I could have just bought an S2 instead.

 

[Suffolk944]

Exactly, the "old style" boost is a major part of the character of the car and always puts a grin on my face. I have lost some of that on-off power delivery with the mods but its still there and I certainly would not want to lose it altogether !

 

[zcacogp]

ORIGINAL: poprock Without it I could have just bought an S2 instead.

Really? [] Oli.

 

[barks944]

You wouldn't necessarily loose that, just shift it down the curve. You will still have the progression from off to on boost....

 

[DavidL]

The main reason for me asking this is that RPM have a LR 340 kit available. I have decided not to go for it but if anyone else would like to consider it then it is available for 1500. Fitting by Promax (who deal with LR anyway) would be around 25-30 hours so around 1750. They are happy to do so for this particular kit. Bear in mind the kit direct from the states is $4000 so around £3400 with duty etc so it is a good deal. In the end I just couldn't justify the rest over a good S2 kit but I may be missing a trick. Hope someone is braver than me.

 

[DivineE]

ORIGINAL: barks944 You wouldn't necessarily loose that, just shift it down the curve. You will still have the progression from off to on boost....

If anyone on here owns it I would recommend you go for a spin in the black RPM turbo that was recently sold before you make your choice. Even Simon P's Red turbo was heading that way. I think you need exactly as TTM suggests something about GT30 size with a 76mm A/R and .86 hotside to keep the 944's character with a BB turbo. That way you get a little more turbo assist everywhere than standard (which I like because it means a lighter throttle at slow speeds) but still get a big exponential surge of power from just over 3000rpm up which reminds you your in an 80's turbo[] ...only trouble is Simon SPS tells me fitment of that turbo is pure hell and he would know as he tried this on his first car. The most sensible solution is to buy one converted to use the KKK hotside... which is £1500 or more.. but then you need the injectors, 3inch downpipe to make use of it, full exhaust, probably a maf etc etc there's no cheap easy solution [&o] I'm almost totally certain I'm going to put my BIG intercooler on a standard turbo and wind the boost up to 1.2 bar so I'll stick it on a dyno and report what effect that has in a couple of months.

 

[barks944]

Will be interested to hear how you get on with your intercooler. I had a local Landrover tuning and fabrication company near me weld a new end tank onto my IC and it made the spool up noticebly quicker. When I take the snorkel off the air intake car spools up very nicely indeed. I think the first step in all this is the engine management system. Ive been looking harder into creating a replacement digital board for the 944's DME. I think I understand the circuitry now and the only issue I have at the moment is with the reference sensor circuitry. It uses a special timer chip to generate a binary signal from the saw tooth signal produced by the flywheel sensor. Its not an especially complex problem but it will take me a little while to come up with a solution. I hope to make use of all existing wiring simlpy replacing the AFM with a 4 pin 5v MAP sensor. I have also found a clever chinese chap who can help me write all the code!