Oneoverwrx

Hey guys i have been searching around a little this morning for the limits onb a stock redtop. I have found people making 350-375 with no issues but I have yet to find someone who says i have made xxx at xx psi on a stock motor.

Reason for me asking is because i am tuning a buddies car with a 2871 with a .86 housing. Car has all the supporting mods/ bolt ons. Car has a little headwork but is still on stock cams. We are tuning with an safc. He is on sti injectors and a walbro pump. He has a nismo fpr but it is not on the car yet. The car is not a daily driver and we literally have race gas at the pump less than a mile from his house. My question is what is the safe boost limit for this car? Also can you max the stock motor out with pump gas boost(like 20psi) or would he benefit from 23-24psi and some 110oct. I am sure we would be at the limit of the efficiency of the turbo at that point but would the motor take it. Should i tune it on 93 to something like 15psi and then maybe tune a mix of pump and race to something like 20psi to be safe of what?? He is wanting 350+ and isnt wanting to build a motor until after this summer. Any help would be great.

Thanks
Phillip

nevaland9

GT2871Rs arnet that efficient above 20psi & if you love your turbo you wouldn't do above 20.

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punxva

well it will last longer if you tune with something other than a bandaid, aka SAFC... it can be done, but the feeling is always in the back of your head is it going to blow when i get on it. do it right, be a good friend

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Monooxide

There is a guy who made 395WHP @ 19PSI on a GT2871R and stock block with cams, the exhaust housing is around a .7* A/R(extrude honed).

http://forums.nicoclub.com/zerothread/213470

jspaeth

People can safely make 400 hp with stock bottom end, and of course, cams, springs, retainers, RAS.....and usually the boost pressure is around 20 psi.


Take 1 psi drop through intake to compressor....so intake air is at 13.7 psi.

Take 1.5 psi drop between compressor outlet and IM, assuming you have a good quality FMIC.....

http://www.turbobygarrett.com/turbob...-15_comp_e.gif


If you look at the compressor map versus airflow, you are best off near a pressure ratio of 2.5 psi, as the map extends farthest to the right there, and you spend a great deal of your time in the high efficiency part of the map

2.5*13.7=34.25.....34.25-13.7 = 20.55 psi.....

Now, that's at the compressor outlet.

Subtract off 1.5 psi across the IC and piping to the IM, and you get like 19 psi at the IM.


Again, if you lose 1 psi in intake, and 1.5 psi over intercooler, a 2.5 pressure ratio gives you 19 psi at the intake mani, or 20.5 psi at the hotpipe.


This seems to agree very well with the fact that most people don't run the 2871R a whole lot higher than 20 psi or so.

If you lose less pressure in your intake, then the corresponding "most efficient" manifold (or hotpipe) boost is higher, whereas the converse is true if you lose more pressure in the intake.

Also, if you are losing more pressure across the intake manifold, and measure boost at the intake mani/coldpipe, then the "most efficient" boost number also goes down......if you are measuring it at the hotpipe, the number doesn't change in terms of what you are reading on your gauge, and you then lose that many psi across the manifold.


I think it's best to measure boost at the manifold, but be conscious of the fact that the air coming out of the compressor is actually a psi or 2 or 3 higher than what you are reading.

I.E. on a T25, boost limit is like 14-15 psi. If you try to do this, but are measuring boost on the coldpipe, you are really running the turbo at 16 psi+


Obviously a lot depends on how much boost you lose through your intercooler

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scooz14

you should get something to monitor detonation, or pre ignition. as long as your are not getting any knock, keep pumping up the boost.

jspaeth

^ Wrong.

Just because you aren't getting knock doesn't mean it's not bad for the turbo or bad for your motor.

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GabeS14

The stock motor will take 400 hp but I wouldnt be boosting 23-24 psi on stock motor, its like testing its limits.and the turbo's too.and for what?
keep it safe till you do some supporting internal mods, and decent tune.also you need a external waistgate to be able to boost that hi on the 2871
I would do 19-20 psi max on it even if done right...just because someone else made 400hp on stock motor doesnt mean your motor will hold up.

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Flybert

Just get some cams and valvesprings or 330whp is going to be the limit.

Oneoverwrx

punxva- thanks for answering the question. I love safc haters. LOL

jspaeth- Thanks for the informative post. I am thinking going to about 17psi for right now and tuning to a 11.2-3 afr for now. I may have him mix a gallon of 110 in to a full tank of 93 just to be safe. It should raise the oct a point or two just for safety.

He does plan on doing cams soon i was just trying to get him something to work off of.

thanks everyone for you answers, i appreciate you all not telling me to search as i assure you i have done plenty of.

jspaeth

SAFC = :ghey: with big power setups, but I guess for now it will have to do.

With that much power, a standalone or at worst rom tune should be the way to go

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Oneoverwrx

well i have had really good luck with an safc. I actually tuned an safc on a 50t srt4 last week and it made 416 on pump gas.

slider2828

It really depends I ran good 11.5 on 91 pump on my 2871r with stock bottom end. Ended cracking the edge on my stock piston... Maybe .5 inches at most. No Scoring no nothing on the side walls... It just all depends... I was running 16psi at the time. What can I say, you really push it... I ran a T25 at like 12 psi and the turbo blew.... BUt none the less... I run 17 on a built bottom end now.... and built head...

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Oneoverwrx

ok guys.....some new news. He weighed the car the other day and with lightley stripped interior and 1/4 tank of gas the car weighed 2420lbs. Which got me thinking that his car was going to do well at the dragstrip. He has a welded diff and 26x8.5 MT slicks So it should hook up and last night i had my buddy with the 416whp srt4 race him and on a roll the were very evenly matched. The neon would start to pull away above 125 or so but up until then they were very close.

Question: What do 2871 guys run at the track? I am thinking he is going to be trapping 117-120 after last nights race. I am thinking he is going to be around 11.70 or so??AM I close at all?

McRussellPants

OMG.

what the fuck is this thread.

2871 will make power and be happy all the way to 24psi. particularly the .86.

SAFC omg SAFC omg.

Drag Racing 5 runs a month or something like that You Could probably run a Stock Internal Motor up past 450. I wouldn't dick with it, and wouldn't touch it with an SAFC.

stock cams and intake manifold your gonna be making around 350 no matter what you do. so you might as well just run 20psi though it for now and bump it up later.

corriganjoshua

There are so many factors that come into play once your actually at the track its hard to make a real accurate prediction.

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steve shadows

Wow McRussel you sound like me?

Haha / thread

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surge s14

whats the stock spring for a 2871r set for? im in need of a new turbo... can i just bolt it on i need break in time

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jspaeth

Depends on which wastegate you have.

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punxva

i'm not really hating on it, ive been running one on my Ka-t setup and am just telling you from personal experience that with higher power levels you want to go ahead and just get a better form of tuning with my control other than hacking the signals aka safc and btm

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Z U L8R

i wouldn't push it over 17-18 on 93 octane and wouldn't go passed 22psi on 110 octane, if all you got is an safc2....you're off to a bad start, with that said, if that's all you're gonna use to tune with, back the base timing down at least 2 degrees aka 13 degrees advanced instead of 15, and i recommend RAS.

my .02
Dave

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FusionR240sx

i wouldn't go past 15psi with a stock paper thin headgasket

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bigOdom1

this thread is full or fail with a spoonfull of useful information

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my car domain

that good review thread

surge s14

what about the internal wastegate it comes with? (t25 inlet)

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steve shadows

Really? Show me the point on the surge island where it's totally tanked at 20psi?



I would feel comfortable pushing the 2871R out to about 22 psi max.

On a stock motor, on pump gas with a Front Mount Intercooler, 16 psi is safe.

I usually won't tune over this point, mostly because the gas we have here in cali is 91 octane and because the cams just won't let much more air in.

Camshafts are really the door keeper of cfm or airflow into the intake side of your engine.


A front mount intercooler is really mandatory over 250whp ranges. We have been doing heat soak tests with side mounts vs. cheapo ebay fmic on some of the car's lately using an IR gun. The Side mounts overheat completely after 1-2 passes. Just think about that when your trying to road race? all that hot air.

A good fmic mandatory (with decent placement and air flow) for saftey with your tune with regards to setups like the OP is talking about.

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makdaddynuge

not meaning to thread jack, but STEVE SHADOWS, how were your ebay intercoolers doing?

Oneoverwrx

We now have an apexi hg on the car and are going to go to the track this friday. We are going to try to run about 18psi on a mix of 93 and 110. This should definately eliminate any knock and keep the afrs a little on the richer side. After this we are going to do cams and possibly an intake manifold. Might send a stocker to get extrude honed. Has anyone had experience with that or is it better to just buy one like the greddy?

Blown240sx

Oneoverwrx where in KY are you located?

Also richer isnt always better. Too much fuel can cause issues also.

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Oneoverwrx

I am in richmond. I know richer isnt always better. But if it is in the mid 11s on race gas with absolutely no knock i doubt we will have a problem. I was just saying i wasnt going to tune it on the edge even though we would have the cushion of the 110 octane. I had it at 11.0:1 all the way acroos the board on 93 at 14psi and it was really strong so at 18psi with some 110 and some minor adjustments it will be very safe.


Where are you at? in ky i assume.?

Blown240sx

Bowling Green

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