mdj577

Have a manual boost controller and new wastegate from Lindsey (as well as chip, fpr, boost gauge). I am not clear on boost though.

According to Clarks the 951 comes from the factory with a 1.75bar (~25psi) max boost.

I read a recent thread (https://rennlist.com/forums/944-turb...u-running.html) where many mentioned that they run significantly less boost.

Question: As a starting point should I try to set myself at 25psi to duplicate stock values, or lower. Should I expect to see a significant performance increase because I am using a new wastegate, chip and returning to factory boost limit will just multiply the power output?

Dougs951S

25 psi lol... a stock car makes about .75 gbar, you are misunderstanding the factory spec of 1.75 bar, which is an ABSOLUTE measurement, meaning .75 bar (~11 psi) gauge pressure. What sort of chip are you running, for older chips thats usually what dictates your boost level. Get an air/fuel ratio gauge, install it, install a 3 bar FPR, and then try upping the boost to about 1 bar, that will put you at ~315 hp at the crank, which is a significant increase over the stock 217. It's pretty easy to get these cars up to about 335 crank HP on the stock turbo, after that it starts getting a lot more expensive to play. BTW if you just got the car, you should do the timing and balance belts, which is a good time to add a 4* advance cam key, which will help spool up and low-midrange torque with the stock turbo.


FWIW, here is, in my opinion, how the game goes:

Stage 1: 3 Bar FPR, performance chip of your choice (hint, get the rouge A-tune), manual boost controller, AFR gauge, DP wastegate--- ~$750-1000, ~315 hp
stage 2: 3" turbo back exhaust, FM intercooler, bigger turbo, bigger injectors, MAF kit or standalone ECU: $2500-3000+, 400-450 hp
Stage 3: head work, fuel pump, cams, 16v conversions, stroker/big bore engines, ect: $$$$$$$$, more power than you need

If you do everything from stage 1 and 2 you'll have a mighty fast car on your hands that will straight up murder 90% of whats on the road today in a highway pull (simulated, of course). Keep in mind also that past ~375 hp, the stock clutch gives up the ghost so also factor in the cost of a new performance clutch if you intend to push the limits of the stock internals (the fuel pump is good to 400 hp, the stock forged rods are good till about 450 hp).

All in all, expect to drop 4-5k dollars bringing a stock car up to 350+ rwhp (a stock 951 dynos ~190 rwhp). I know you didnt specify goals, but boost is addictive so I wanted to spell out the big picture. After that, expect to drop a few more thousand getting the suspension up to snuff. These cars are cheap to buy, but expensive to maintain and play with. Pretty easy to spend equal or more than initial purchase price on mods, after getting basic preventative maintenance up to date of course.

mdj577

That makes a lot more sense. Looks like I should keep the pressure down around the 15psi range. I have had the car for about a year and it is stock besides a FS full exhaust (cat delete). Going to gradually get it up to around 350rwhp.

Thanks for the info!

Willard Bridgham 3

To start, know that the boost gague is in PSIA and at 1.75 bar is running 10.75 psig.

Dougs951S

No problem. Pro tip, if you want 350 rwhp, just do it right and do it once and never look back. Forget "doing it slowly". Buy the biggest turbo you can deal with lag wise, slap on some 80# injectors, then megasquirt it and turn up the boost till the clutch slips. Boom, 350 rwhp, and you can do it for 1500 bucks. (the bit about buying the biggest turbo you can was kind of a joke, obviously but you wont get 350 rwhp reliably on pump gas without a pretty decent sized compressor, probably at least a 54-57mm)

mdj577

Sounds good. I am going to see how the car behaves as a street vehicle as it is (3" exhaust/cat delete, fpr and lines, WG, MBC, and Lindsey chips). Rest of engine/drivetrain and suspension is in good shape and stock.

The plan next is to get everything I can out of tuning the suspension, hopefully without spending ridiculous amounts of money, before doing any more "power mods".


WB3- Thanks, got it.

aglaes

Actually Willard, psia is short for pounds per square inch absolute. The 951 boost gauge is actually bar(a) - bar absolute.

rlm328

The car in this form is streetable and reasonably quick, to do anything else to it is getting in to some serious cash even if you do the work yourself. I would keep it as it is and upgrade the driver and then the suspension before I would throw anything more at the motor and drive train.

Also as stated earlier the gauge in the dashboard measures pressure in the manifold which is the atmospheric pressure plus the boost being produced by the turbo. Note that your atmospheric pressure is affected by a lot of things, altitude and humidity to name a couple.

raleighBahn

Best immediate bang for buck: 968 M030 front and rear sway bars. You can get these new from porsche (for a while one of them was disco'd, but they're back now) or from lindsey (they have great options), pelican, paragon, etc.

Easy upgrade, can install yourself, and you will not have any question the car handles better.

Dougs951S

IMHO front coilovers with stiffer springs are the best bang for your buck mod to any 951 right after a chip and MBC. sway bars should be used to fine tune a suspension setup, its the last thing you worry about after you have your dampers and springs set up.

mdj577

I was thinking along these lines as well: coil-overs first then M030 sway bars. Have had my heart set on KW V3s for a while. I have heard great things about them (easy install, very good performance) but the price has been stopping me.

The other thing I've considered is replacing all rubber bits (bushings etc..) with original OEM stock.

I imagine new from the factory these cars handled pretty well, no?

raleighBahn

I concede the point - on recollection, mine already had the coilovers and springs when i got it (I did the sway bars). But from that point, the bars really dialed it in

Smudo

What would be approximate gains with A tune if you run around 14 psi (stock with KKK26/6)? Something around 230 rwhp? And would there be any difference if I run the same 14 psi with M-tune? As of now the engine is stock. The only modification is 3 inch exhaust (with two Magnaflow resonatiors, without cat and with Tial 38mm waste gate).

Dougs951S

You'll see more than 230 rwhp with A-tune at 14 psi (14 psi is NOT stock, more like 11 psi). To achieve those boost levels, you'll need a boost controller of some sort. Expect maybe 250 rwhp. You'll definitely make more power at the same boost level and have better throttle response with the M-tune. For a mostly stock car likes yours though, the A-tune represents a much better bang for your buck since its pretty cheap for a ~50 rwhp gain (in conjunction with raising the boost).

Zeff

Look up my old threads. I had dynos of a 26/8 w test pipe and chip and then going to a maf. Youll seemore with a maf/ injectors 3bar vs chip and 3bar but not a whole lot more.