help, why as i go near redline i drop more boost?????????????????????
 

Ok first when i floor it and get on the boost, it shoots to 7.5-8psi depending on load and ----.. then it levels out around 7psi then 6.8 or so.. then as i approach redline it goes to around 5.5 5.3 psi!!
why the hell is it dropping like that? what is the cause???

ihi rhb5 internal wastegated turbo on a d16y8 with intercooler and 450cc smc 500

Re:help, why as i go near redline i drop more boost?????????????????????
 

turbo had no shaft play and was in EXCELLENT condition... spins really good and this turbo is watercooled so that's why it's in good condition... stock WG is around 8psi i have heard... with my intercooler i should be hitting 7psi or so...

Re:help, why as i go near redline i drop more boost?????????????????????
 

The only thing I can think of of is that your out of the efficiency range

Re:help, why as i go near redline i drop more boost?????????????????????
 

mine does that too... d16y8 w/ t25 set at 9psi.
i think its the waste gate. also it varies in different gears. must be wastegate related.

Re:help, why as i go near redline i drop more boost?????????????????????
 

ok have you tried putting the WG signal line right at the manifold??? or at least after the IC?

i'm going to try someshit like this and see if it'll help

Re:help, why as i go near redline i drop more boost?????????????????????
 

consider the fact that you two are using tiny ass turbos

Re:help, why as i go near redline i drop more boost?????????????????????
 

yea your out of range for your turbos i test drove a saab the other day and it fell out of boost at like 5200rpm but was fully spooled by 2100rpm it was to under sized for the big 2.0litre in them. so its the same thing your having. just need a bigger turbo!

Re:help, why as i go near redline i drop more boost?????????????????????
 

ok if i pull my wastegate vacuum line, the turbo should boost to heaven right?? maybe at least 15-18psi even at redline...

sooooooooo... if i get some boost controller, then it'll up the boost accordingly at higher rpms to accomodate the higher flow right??

Re:help, why as i go near redline i drop more boost?????????????????????
 

no it will still hold the same to redline, but spike real high at low rpm=bad idea

Re:help, why as i go near redline i drop more boost?????????????????????
 

i don't belive my turbo with the wastegate CLOSED will only give me 5-6 psi at redline on my dinky d16 engine...

my friend holds 7.5psi to redline on same engine...

do you think it's boost leak somewhere?? how can i check this???

are dsm 1g bov ----?

Re:help, why as i go near redline i drop more boost?????????????????????
 

they are right; its past its efficentcy point. Where do you redline at? At what point does the boost go down? Its a tradeoff of a small turbo; less boost at topend. Im putting a teo4h on my teg and people say its too small and crappy. Maybe you could try shifting eariler ahhaha. Small turbos are great for autox but it bumps you up in class :-\

Re:help, why as i go near redline i drop more boost?????????????????????
 

redline 6900 rpm ONLY

1.6 S O H C vtec small engine


it drops like 5500 or after vtec on 2nd gear.. 3rd i don't think it drops much

could this be boost leak?

Re:help, why as i go near redline i drop more boost?????????????????????
 

does it feel like its loosing much power towards redline or just that the boost isnt as high

Re:help, why as i go near redline i drop more boost?????????????????????
 

dunno, everything is pretty fast at higher rpm....

it's still boost.. like 5-6psi.. not like NO boost.. yeah it feels fast still

but watch my wording... "FEELS"

Re:help, why as i go near redline i drop more boost?????????????????????
 

im leaning towards the turbo being to small. when does it spool

Re:help, why as i go near redline i drop more boost?????????????????????
 

where is your wastegate actuator line sourced from? Put it on the intake manifold so it'll keep boosting till you make 8psi in the manifold.

Re:help, why as i go near redline i drop more boost?????????????????????
 

take off your air filter see if that does anything. seriously.

Re:help, why as i go near redline i drop more boost?????????????????????
 

ok starts to spool almost like 1500-2000 rpm.. fully by 3000 or so....

wastegate line is RIGHT OFF THE COMPRESSOR

filter??? hmm.. i'll try all of these...

Re:help, why as i go near redline i drop more boost?????????????????????
 

try sourcing the WG from the intake manifold.

Re:help, why as i go near redline i drop more boost?????????????????????
 

if u run with no waste gate line your bov is still going to blow off at its set psi unless u have a aftermarke one. ive seen alote of stock cars with the wastegate line ran right off a charge pipe but that would be the same as the intake i suppose. but if your still making some boost till redline then thats what it should be doing. all stock turbo cars do the same. g/f's vdub makes 8psi from 3g to 5800rpm then it slowly falls off red line is 7200 on the car by the time u shift its making around 4-5psi but is still pulling hard all the way thru. i think your set up is fine.maybe try a bigger turbo and see what it does but i think your in good shape

Re:help, why as i go near redline i drop more boost?????????????????????
 

bov's dont have a set psi...shitty ones leak if thats what you mean, and spring tension is adjustable on some, but that would only really affect max boost, not make it drop over the rpm range

Re:help, why as i go near redline i drop more boost?????????????????????
 

well im going off of the 3 hours worth of ---- tunning i had with that vdub i talked about put a damn boost controller on it and it would blow off at like 3400rpm when it was making 12psi ...pissed me off cause now we have to buy a new bov

Re:help, why as i go near redline i drop more boost?????????????????????
 

more observations:

4th gear today, i pulled 7psi or 6.8psi near redline.. didn't drop much.. 3rd gear.. about 6.5psi... 2nd gear DROPS TO 5psi.... hmm .. i couldn't bother 1st gear...

so you think maybe my engine ins't producing enough exhaust pressure to spin it at lower gears??? not enough load??? this is bullshit my engine

Re:help, why as i go near redline i drop more boost?????????????????????
 

ey peoples TOO SMALL of turbo...

my car wont go over 3,000-3500 rpm..... So.....

The higher revs the more your boost will fall. you max out a tiny turbo like that fast. pick one fast spool or high end.. high end t3 fast spool t25 tdo4 14b want the best of both worlds work a t3/t4 hybrid out. Look at the compressor maps in the top links.

Re:help, why as i go near redline i drop more boost?????????????????????
 

Keep in mind that it's not all that bad to lose a little boost at the high end. That's usually when bad ---- happens anyway. I would be pretty happy if I were you.

Re:help, why as i go near redline i drop more boost?????????????????????
 

reign: yea sometimes you get a little less boost in lower gears and more in higher gears

ineedturbo: yea stock bov's on those cars leak, its not like they are set to do that, just a weak spring/design

Re:help, why as i go near redline i drop more boost?????????????????????
 

Those turbo's are small..maybe you got a small downpipe or restrictive exhaust.
And a 1.6L isn't small though put the turbo on a D15 and it would be ok

Re:help, why as i go near redline i drop more boost?????????????????????
 

thanks for the info ghettoturbo...

Re:help, why as i go near redline i drop more boost?????????????????????
 

so it's ok.. i hit say 7.5 at first.. then drops to 7 around 5500-6000... then maybe 6.7 around 7000

it's good eh?


like don't we want our peak HP to be a bit b4 redline? i see all those dyno graphs, the TQ and HP on turbo cars usually drop off like 1000 to 1500 before redline...

say redline is 7000... turbo spools 3k

max hp usually is like 5700-6000 rpm then drops... tq drops same but tq max is like 4200-4500rpm...

i dunno man