Hi guys,



well, idk why, but the highest boost i reach is 7-8 psi in 3rd. gear around 5000rpm, even in 4th gear i dont get more than that.



7,5psi are standard for the S5.. but thats the weird thing.. here my modlist:



1991 S5,

Porting-Job by ArmyOfOne

big/wild streetport

ported exhaust ports

ported intake-system

modified throttlebody

Stock turbo with ported WG

FULL racing-beat exhaust system (w/ presilencer)

APEXi Power FC without MAF and APEXi cone filter.

800cc Secondaries

HKS SSQV BOV



rised oil-pressure and all such stuff.. in fact i should have at least STAGE III of FC3SPRO.COM "From mild to wild" (porting not included)

and we expected at least 12psi of BOOST.. my desired boost was 13- max 14psi

but like i said above.. NO CHANCE for higher than 8psi..



I hear no boostleaks, and the BOV seems to be leakproof, so i have no idea why i get such low boostlevels.



Do you have an idea?



Well, the car runs very nice and has much more power than stock (thanks for the great Porting from ArmyOfOne https://www.nopistons.com/forums/pub... )

but it seems it could be even a bit faster with 4-5psi more than at the moment https://www.nopistons.com/forums/pub...#>/biggrin.gif



thank you very much.

maybe i missed something here, what boost controler are you using?





randy

oh i am sorry, i am using NO boost controller yet! because WG is ported and with the mods we have done we shouldnt have more boost than 12psi anyway.. and 12-13 psi was my desired boost, so it means i dont want to go further anyway.. but i want to buy a boost controller for sure. i am just wondering why i get such low boost, with all these mods.



well my last FC s5 had 10,5psi with just a F.C.D. a cone filter and the full racing-beat exhaust (no ported WG) and the actual car has much more mods done on it, and especially the ported exhaust ports should rise the pressure a little bit, but i only get 8psi maximum.. which is just 0,5psi more than stock pressure!

Get a boost controller. The ported wastegate actually helps you maintain the closer-to-stock boost level.....

i was wondering if it is so.



what you mean is, for example:



FULL exhaust with testpipe without WG porting , up to 10psi

same with WG porting, prevents "overboosting" and keeps the boost at 8psi because of the WG port which can flow more exhaust?



thank you for your replys

just a thought ..you said that your running 800cc injector , maybe if its not a leak it may be too rich in tunning ..just a thought

oh! well, i am not THAT rich, but thank you very much for the hint.



my settings right now are ~11.3:1 during 0,55kg/cm² (7,8psi) and about 11.7-12.0 during 0,2kg/cm² (~3psi)



i have to setup the mixture and ignition myself, because i want to learn all that stuff, and dont want to LET it tuned by a professional, because on that way i will learn nothing.

in fact i am very satisfied with my current maps and settings, and i always try out new settings. was just wondering about the low boost.. but as mentioned up there, it cant be too rich, because during the "high-load" where it should go up to 10psi or even more, i have an AFR of max. 11,4 and min. 11,2

yeah since you are running of the wasgate spring it it boosting around stock the porting of the waste gate makes it easier for the wastegate to relive excess exhaust pressure while why you did not have it ported it would be harder to relive the exhaust the turbine would get more exhaust and cause more boost.your best bet is like what was said above get a boost controller even a cheap manual one will do on a stock turbo

thank you so much!! i have asked several people about that WG porting thing, because i was sure its the cause! like you said, its easier to relive excess exhaust pressure. but there were several people mentioning that the porting has no effect to the boost level..

now i know i have no boostleak at all. boost controller here i come!



hey well, one mor question. my mod list is above. like you should know, the boost drops about 6700rpm on the stock turbo. could i keep it boosting with a electronic boost controller like AVC-R or EVC?

I know i should get a bigger turbo for high-rpm boost, but all i want to know is, if its possible to keep it boosting around 7000-8000rpm.

AND make it even more boost in 2nd gear, as because of the construction of the turbo and its "lag" the rpm rises much faster than boost pressure (which is total normal) just want to know if i could improve that, and build up more boost in 1-2 gears with an electronic boost controller.



thank you very much https://www.nopistons.com/forums/pub...IR#>/smile.gif

I hadnt been online in a little bit - so i wasnt able to backup my ported wastegate comment, but i see others did. This is typically a good idea when you have a mostly stock car. Getting higher boost because the stock WG is not ported is just a side affect of the modifications, doesnt mean you WANT it to do so on its own. Having the ported WG and adding a boost controller will be the best bet. An EBC is not really needed as it performs the same as a MBC and the MBC is way cheaper. The EBC advantage is simply in convenience. I find them to be way to tempting though and on mostly stock cars, the MBC is safest, lol...



The stock turbo will roll up to 10psi with the MBC in place.... if its falling on its face at 6700 than that can be your tuning or just the exhaust setup, etc... I wouldnt go much past 9psi on the stocker anyways, if it goes, it might take the motor with it...

hey, thanks for your reply.



why do you mean it would take my motor with it, past 9 psi? I think my motor should handle a bunch more, but my turbo wont make it that long i think.



hmm.. my map is 11,3AFR at 8psi, threw the whole boost area (8psi) until 7500rpm. My exhaust is a full racingbeat with a presilencer, and the ignition map is almost stock, so i dont know why i got lower boost levels from 6700rpm :( could it be the ported WG also? idk!



anyway, thank you very much for backup that WG thing, now i know i was right, and that i have no boostleaks at all, but its naturally that i dont get boost rise with a ported WG.



ps. i dont want my stock turbo to last forever, just 1 year or something like that. since there are guys running them with 14psi, i was sure to be safe with 12-12,5 psi. and if the turbo is down, i was going to go with a BNR St.3

I was referring to the fact if the turbo should fly apart, the compressor wheel will go first, and tiny bits of metal inbetween the housings and rotors usually dont vote well for the longevity of your engine.



As for the boost level - 9psi is optimal.. 10psi is ok, but those guys running 14psi on the stock turbo need to learn how to read a compressor map, the stock turbo has no guts really past 10psi - those extra 4psi are just hot air, lol...

oh i see.. thank you very much for this advise! i didnt know that.

Well ok, than i will be going to run 9-10psi, and just wait for an other turbo lol

Thats the safest bet - 10psi will still make plenty of power for now.



There was a guy around here who made 298whp on the stock turbo at 10psi I believe. He did have a ****-ton of motor work though, lol...

that was our purpose also, getting around 300whp. so i cant await the dynorun after i get a MBC

Hey, could my boost loss in higher rpms be caused by high air temperature? (50°C) or restrictive intake?

the only restriction right now is the stock mount intercooler.



i have no MAF, the throttlebody is modded, and the UIM/LIM are ported.

Are you referring to hot atmospheric air - or how hot your intake temps are?



Restrictive intake systems can limit boost, but with a free flowing air filter (thats clean) you shouldnt really have any bottlenecks that would keep you away from 10psi. Fuel and timing play the bigger factor at the higher RPM to maintain boost... provided you've got a good breathing turbo.



Have you confirmed that your turbo is in good shape?

Yea, the shaftplay is just normal, there are no oil-leaks and no smoke coming out of the exhaust at WOT. Also it spools up quick to 8psi at 5000rpm and holds it until 6200~

then it begins to drop.. some kind of that way:



6000rpm 8psi

6400rpm 6psi

6600rpm 4,5psi

from 6700 it holds ~3psi up to 7800rpm



I noticed weird AFR readings at high-RPM also.. as told my MODS above, i have 800cc secondaries, and my AFR are setup at 8psi running 11,4:1 and it keeps that value until high RPM are reached, lets say 6800rpm. THEN the mixture gets leaner and leaner. You will say, YEA because my map is to lean in that area..

but its not the case, my map is setup richer and richer, but it gets lean anyway.. something like that:



6000rpm 8psi AFR 11,4

6400rpm 6psi AFR 11,6

6600rpm 4,5psi AFR 11,8

6800rpm 3psi AFR 11,9

7000rpm 3psi AFR 12,1

7400rpm 3psi AFR 12,8

7800rpm 3psi AFR 13,5

8000rpm 3psi AFR 13,9



My PowerFC map is at MAX in that area, and the Injector duty is at 74% MAX.. i can only richen it up by using a trick, in telling my MAP-Sensor to inject 110% in the 7000-8000rpm area instead of 100%, then i get 11,8AFR readings at 3psi of boost.

So i wonder what causes this lean mixture at highrpm, but with rich map and, 800cc secondaries, walbro fuelpump, AND since my boost gets down to only 3psi, it should even get richer and richer and not the opposit right?



And thats where i say, it cant be a rich mixture right? because i get such sucking AFR in that rpm-range.. or is it a phenomenon that you get LEAN reading if you are TOO rich? i dont think so.. my LM-1 wideband is showing me even 7:1 readings if it must.



My ignition timing at such pressures and rpm are as follows (degree ATDC of course):



5600@ 8psi 17°

6000@ 8psi 17°

6400@ 6psi 21°

6800@ 3psi 29°

7200@ 3psi 30°

7600@ 3psi 32°

8000@ 3psi 32°



i had BASE ignition-MAP before, and was experiancing the exact same boost loss.. so i dont thing its my current ignition-timing that i am using, which causes it.. :( if it only would be the ignition, at least i would know what i am doing wrong.. so here is the BASE-Map:





5600@ 8psi 12°

6000@ 8psi 12°

6400@ 6psi 15°

6800@ 3psi 24°

7200@ 3psi 25°

7600@ 3psi 27°

8000@ 3psi 27°



SPLIT is 10-8° in this area

Well..



The tune looks good, but let me ask this - how different is the port timing on this engine from the previous one? Port timing can affect your peak HP and cause the stock turbo to "run out" before a normal stock port would... does this make sense?



If you blow through a 1/2" straw as hard and fast as you can, you'll feel that pressure build up in your cheeks... but now blow through a 1.5" straw as hard and fast as you can - all the air will escape very quickly and NOT build as much pressure.



Its a terrible way to describe it, but does that make sense?



Thats why bigger ports usually run larger turbos, the larger turbo will "push" more than the engine can hold thus building pressure quicker and longer....

ahh, i see. thank you, i wasnt thinking that way, but it makes sense.



well, the porting on the front and rear iron is about 2mm to the side (towards rotorhousing) and around 5mm to the top and over the upright edge, no way down at the bottom.

some porting to the intermediate plate, ported LIM and modded throttlebody (pulled out the first plates)

the exhaust is ported to the bottom and the sides, but not to the top. this because of emissions which i have to go threw.

It's hard to say - but I would guess that would PART of why you arent seeing boost all the way to readline with a stock turbo, the nice thing though - when you get a new upgraded turbo, that porting will help the bigger turbo make its power all the way to redline https://www.nopistons.com/forums/pub...IR#>/smile.gif

which turbo do you think is best for response and the porting i have?

i was thinking of going the plug and play way, and wanted to upgrade to BNR3.

but it would make no sense if its not the perfect solution for the porting i have.



i am not up for dragracing, but circuit and highway (highspeed)

hey, after reading a post from Lynn, i think i got what you were up to tell me.

You meant, if the runner (i think i call them right.. (the "tube" from LIM to the intake Port) is incrased in volume, its like a bigger straw and slows down the velocity of mixture going threw it. am i right?



if i am right.. i have to tell you that my runners have got some porting, they have much more volume over stock!

could THIS be the reason for lower boost at high rpm?

That could be a factor - probably not the entire reason.



As for the turbo - a stock upgrade would be good. You should use at least a 60-1 compressor side on a large sp IMHO..

BTW - i think the BNR3 is a 60-1 - not sure though....

yea it is, and the BNR mod can be used up to 17psi as far as i know.