sr20boi

im going to get this turbo installed in my ride.gt2871r. i have a redtop sr20det stock with just exhaust and pullies and a short throw shifter. i want to know if its okay to run it like this with out my fuel upgraded..???? will it start to fuck my shit up and start driving shitty??? I wont be ragging on it untill i get that done though..Thanks.

jspaeth

If you are on stock maf and stock injectors, you CAN "drive" the car, but I would not let it build boost beyond 3 or 4 psi or whatever, or else you are gonna probably cause damage.

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confuzed240

Had this same set up. DON'T BOOST. Air fuel ratio look like an N/A at 7psi. Its going to run like shit too FYI.

sr20boi

so i should just drive it easy? i have no other car so im going to have to be driving it.. and ya i do have all that stock. thanks for the info.

s14unimog

these posts make my brain hurt... Don't do it dude, just keep it stock and learn about what's there, how it works, and what's involved with upgrading before you grenade something...

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sr20boi

i would but my stock one has blown turbo seals so its a must that i change it..

jspaeth

Everyone that is saying "don't do it"............well that is not quite fair.

If he LISTENS and does NOT boost the car above 3-4 psi, it will be FINE.

He CAN still use the car for cruising and should have no problems.

On a MAF based setup, it doesn't matter HOW you get the airflow, all that matters is the mass air flow of air into the engine.


A GT2871R at 3-4 psi or less will not produce more than 230-240 hp worth of air, which is what you can safely run with the stock T25 at 14 psi.


It is fine. Just don't boost it more than 3-4 psi.

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project7x

well i would probly upgrade ECU if your going to slap that turbo on. Whats this "get it installed" BS who gets their turbo shit done for them? haha.

Im running the same turbo with 370cc injectors and NISTUNE'd ecu at 12psi on my KA with stock internals. And am having great success. gt2871r is a nice kick in the ass thats forsure.

S13 curtis

best advice on this thread

And YES you can drive it. just dont go wide open with it because you dont have the fuel to support it.

I had a stock sr with a 2871r and it will lean out wide open but you can grandma drive it anywhere with no problems.

LSjauN

THIS

If your just gonna use it for the time being DD'ing it, cruising it around town, non ricer mode, you should be perfectly fine.

If I were you, I'd just get the 2871r, save it, and get a stock replacement till you can afford to get the Fuel management upgrade.

My old Twofarty had a 2871r on it, but i had 650cc injectors, 325lph Nismo pump, 1/4" larger Braided fuel lines, was running megasquirt and was Dyno Tuned on Nistune at 17psi, it was simply amazing.

It'd definatly be worth the wait, if you can do it.

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sr20boi

nice info... if i get my turbo installed by a professional i get a year warranty with it so thats why i dont want to do it myself. i will get it done with in a week or so, so i hope it works out ahaha. i would so wait but its my daily driver so its a MUST that i drive it.. would a fuel regulator make a diffrence?

zurud

warranty only cover work being done which is turbo installation. It is Not for blown motor when you boosting everywhere and everytime.

jspaeth

No don't touch the fuel regulator. Just baby the shit out of it and don't boost it until you get 1) a new MAF sensor (upgraded to Z32...300zx one...) and 2) New injectors and 3) a proper tune.


That is gonna cost you an extra $700-$1000, depending upon if you buy all new stuff or if you buy used stuff, and also on what quality injecetors you get.

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sr20boi

alright thanks... what if i just get a maf and a tune because im short on money for the injectors..?

Ham Sandwich

Well then you're just gonna have to re-tune to the new injectors you get. Like what's been said already, either just install it and don't boost past a few psi for now or get a t25 for a few hundred and don't worry about the gt28 until you have the money to support it.

mattsil80wis

dont forget he is gonna need a fuel pump too

mct3351

You will be perfectly fine running 7 psig (stock wastegate setting) on a 2871 up to 7,500 rpm with a stock fuel system. You wouldnt make any more power at 7 psig on a 2871 than you would with a t28 at 7 psig, beacuse the t28 is still in a decent efficiency range on a 2.0 liter motor at 7 psig and 7k rpm. This is all true as long as all the other "bugs" are worked out (base timing, maf wiring, boost leaks, water temp, injector condition, fuel pressure...etc).

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Walperstyle

Get an O2 gauge in your car so you can tell how your car is running. Then you can start to play with boost, fuel ect.

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jspaeth

Yeah, that makes SENSE!



Please do not give out information that is wrong, unless you want to send this guy $3000 for a motor rebuild when his engine blows.

Two different turbos do NOT (necessarily) put out the same mass air flow at the same psi.

The S14 SR T28 turbo does not flow the same air at 7 psi as a GT2871R at 7 psi, so please do not tell people that.

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mct3351

If you could read a compressor map you'd see that at 7 psig manifold pressure a stock t28 can efficiently and adequatly provide mass/volumetric flow to keep up with a 2.0 liter engine to 7,000 + rpm. Your assumption only holds true when the volumetric/mass flow rate demand (calculated as a function of engine speed, displacement, manifold pressure and intake air temp.) exceeds the cabaility of the t28 compressor. This happens around 12-14 psi when comparing a t28 to a 2871. So, yes 14 psig with a t28 is not the same as 14 psig with a 2871. But, a t28 and a 2871 will provide approximatly equal mass/volumetric flow rates until redline when the flow rate demanded of the compressor is only enough to maitain 7psig of manifold pressure on a 2 liter engine.

Additionally, I personally ran a 2871 on stock injectors and maf for about 6 months. From memory, at the stock wastegate setting the injector duty cycle barely ever got over 80% and the stock maf never read over 4 volts (as measured with a powerfc).

So, as you can clearly see, the stock fuel system is completely adaquate to handle ANY sized turbo/supercharger capable of maintaining 7 psig manifold pressure up to 7,000 rpm with reasonable intake air temperatures (ie. not -40 F or anything of the likes). It however could not keep up at say 10,000rpm (if the engine could spin that fast) or if the engine was larger than 2.0 liters.

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jspaeth

OMG.......please answer this question for me.....


Would you say that you agree with the following statement:

"7 psi is 7 psi is 7 psi.......it doesn't matter what turbo it is, all that matters is that it's 7 psi in the intake manifold".

I would like a YES or a NO answer to that question.

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Daily driven

nevertheless

I have a question what psi should I run at..
freshly built cp pistons/ eagle rods
apexi metal headgasket
arp headstuds
255 walbro
stock injectors tho.
s14 t28

mct3351

"it doesn't matter what turbo it is, all that matters is that it's 7 psi in the intake manifold">No, there are many other important considerations.

To expand on what I said:

"So, as you can clearly see, the stock fuel system is completely adaquate to handle ANY sized turbo/supercharger capable of maintaining 7 psig manifold pressure up to 7,000 rpm with reasonable intake air temperatures"

When you are comparing realistic forced intuction options you would usually pick something at least as capable as what you have, so to simplify the explination lets rule out anything smaller than a t28 (ie. t25 and smaller turbos). If you were to assess the air flow rate demand created by a 2 liter engine between 3k rpm and 7k rpm with 7 psig manifold pressure and realistic intake air temperatures, the fueling ability of the stock injectors and the metering ability of the stock maf are within their limitations regardless of the type of forced induction. When comparing a specific pair of turbos like the 2871 to the t28 you will see that the maximum flow rate possible is greater in the 2871. But, at 7 psi manifold pressure the t28 is well within its range of flow rates at that pressure when installed on an sr20. So, then why would you expect the 2871 to produce more power when compared to a t28 at 7 psi on an sr20? It cannot increase the pressure of the air and keep it any cooler than ambient air. So, all things being identical, a t28 on an sr20 running 8 psi will make MORE power with a stock fuel system than a car with a 2871 at 7psi and 600cc injectors and a z32 maf. Additionally, when comparing the t28 to the 2871 as installed on an sr20 that redlines at 7k rpm, the 2871 wont provide a preformance advantage until the two are push past ~ 11-14 psi manfold pressure. That is where, the torque curve will begin to decline and the power curve will flat line prior to redline on a t28 powered car. The 2871 torque curve will remain flat and power will continue to climb up to redline (disregarding other non relevant to this discussion things like cams and intake manifold geometry). This is because you have reached the limitation of the t28 compressor wheel.

If it's a pretty common fact that the stock fuel system is capable of 250 whp would you expect a 2871 to make 250 whp at 3-4 psi manfold pressure as stated above by you? Would expect a 2871 to make 250whp at 7 psi...I dont think so.

Just because the 2871 has a performance range that is superior to the t28 doesnt mean it will provide an advantage within the performance range of the t28.


Simply put
7 psi is 7 psi (comparing t28 and 2871)
14 psi is NOT 14 psi (comparing t28 and 2871)

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lok

you are fucking stupid.

i have had my sr for 7 years.

i have run on stock maf, injectors and ecu with a wideband and nissan consult data log.

T25 @ 10 psi not maxing out anything with good afr's

S14 T28 @ 7 psi and 10 psi, again not maxing anything and good afr's

2871r .64 @7 and 10 psi " " "...

2871r .86 " " " " " "...

I have tracked and drifted all these setups and still have a perfectly good motor.

VQMaxFan

Ran mine for about 6 months also. didn't drive it too much though. also mine was an hks gtrs if it really makes that much of a difference. Never raised the boost though. I had a wideband and afpr atleast though.

jspaeth

As far as whether or not your OEM fuel system can HANDLE the airflow, this statement may be true.


But the fact is that the MASS AIR FLOW out of those two turbos at the SAME boost level is NOT THE SAME.

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mct3351

So you dont get it? I'm done trying because IMO those explanations are sticky worthy.

"But the fact is that the MASS AIR FLOW out of those two turbos at the SAME boost level is NOT THE SAME." = This broad all encompassing statement is absolutly WRONG! The only slight variance, at 7psi, would be in which efficiency island your on.

To the OP, believe what you want. I will NOT be sending you $3000 if you blow up your stock long block (valued at ~$1000), so you probably shouldnt run more than 3 psi

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codyace

'Runs well' and 'Runs right' are certainly two different things. Kids run 15/16 psi on a t25 without issues, others explode them at 10.

It's not worth the risk, or the minimal gain to push my luck. You're not getting a trophy for running it, and nissan ain't helping you rebuild it if explodes, so why bother pushing it.

What does efficiency islands have to do with total air flow like Justin is trying to explain to you? 70% efficiency on a turbo that doubles the flow of a another turbo in the 80% efficiency is MUCH more air flow and MUCH more power.

7 psi is not 7 psi on anything. t25 to gt35, YSI to F2.

I think what you are trying to say, is that at 7 psi neither the t28 or the gt28xx will blow up the engine...and that's probably true. BUT that's not to say that 7 psi is the same amount of total flow from both. You can NEVER relate BOOST per safe....A t25 car with S3 cams will push everything past the limits, it just flows air like crazy.


So while you may be right about 7 psi not making a difference, your explanation is totally wrong.

Offtopic What I'd like to see is a comparison (albiet it will never happen) of a t25 at 14 psi vs a 28xx at 7 psi to see what has a better average power band....and then measure it across time.

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mct3351

Let's run a little thought experiment. Imagine a majic box capable of unlimited mass flow rate at ambient temperature. Imagine we connected this to the throttle body of an sr20 and asked it to pressurize the intake manifold to 7psi, then took measurements of the mass flow rate as the engine rev'd from 4k rpm to 7k rpm. The mass flow rates measured are measurements of the mass flow rate demand/required to pressurize an sr20 manifold as it rev'd through the rpm range with air at ambient temperature. Remove things like cams, intake manifold and ve from the experiment because we arent changing those things. This majic box experiment is the most ideal/upper limit flow rate required to pressurize the intake manifold, becasue regardless of how effieint a real world compressor is it will heat the air because of the idea gas laws. The power output by the sr20, connected to the majic box, at its peak engine speed will be the peak/absolute maximum power possible, because this is the ideal case. The torque curve will be flat through the rpm range because the cylinders are filling with the mass quantity of air regardless of engine speed. When an intake valve opens the most amount of air mass it can take in is equal to 2.0 liters divided by four cylinders that is pressurized to 7psi. Increasing engine speed will increase the mass flow rate required to maintain 7psi in the intake manifold because there are more intake events in a given amount of time. So the difference is turbos will lie somewhere in terms of flow rate underneath this maximum/ideal case.

Assuming we are using air there are only so many parameters that can affect mass flow rate. Pressure, Volume, Temperature and engine speed. If we are talking about 7 psi manifold pressure and the volume of the engine is fixed as well as engine speed rangre the only remaining parameter that can change is temperature. When a small turbo like a t25 is asked to pressurize the intake manifold of an sr20 to 20 psi it will do so reasonably efficiently up to the mass flow rate limit of its compressor wheel. If the intake manfold pressure does not at some point drop after the mass flow rate limit has been reach that means that it has begun heating the air. Usually what happens when the mass flow rate limit has been reached is a combination of unnecessarily heated air and the intake manifold pressure will drop.

So when comparing the two turbos a t28 and a 2871 as installed on an sr20, they are both capable of producing adequate mass flow rate to pressuize the intake manifold of an sr20 to 7 psi without adding excessive amounts of heat or droping the intake manifold pressure near redline. Yes there will a slight neglible difference in the neighborhood of < 3-5% percent probably (I hope thats not what you are arguing for). But, at 7psi the engine's "pumping" ability will be the mass flow rate limitation. Between the two turbos this is not true at 14 psi. That is when your absolute rule that Xpsi is not equal to X psi becomes true when comparing these two turbos or any other turbo at least as big as a t28 upto and including a t88 on a 2.0 liter.

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jspaeth

How much horsepower does a SR20 with a T25 make at 15 psi?

The same stock SR20 with a 3071R at 15psi?

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